I did this hike as a three-day backpack. 

Day 1:  Trailhead to Lewis Meadows, 11 miles.  When I reached the parking lot at 9 a.m. on a Monday, there were plenty of open spaces.  This contrasted sharply with the scene on my return at noon on Wednesday, when the lot was jammed and drivers were backed up waiting for spaces to open.  So arrive early!

The sky was overcast when I started, but became partly sunny as the day progressed.  The trail wasn't too crowded at that hour, and I soon left most day hikers behind.  I met a few other parties of backpackers.  The trail as far as Lewis Meadows was in generally good shape, but there were a number of puddles from the recent rains.  There were no blowdowns. The Hoh Rainforest was, of course, gorgeous, particularly the moss-draped bigleaf maples, whose foliage was starting to turn color.  There are only a few views of the river itself from the trail.  At one point, I heard an elk bugling, and I glimpsed a cow elk crossing the trail ahead.  My only other wildlife sightings were sooty grouse, a few frogs, and several blacktail deer nosing around my campsite.

Five Mile Island Camp looked like a nice place to stay:  open meadows, a privy, and plenty of room to spread out.  Another .7 miles up the trail is Happy Four Camp, which I checked out.  It's much less appealing, just an alder thicket with a few clear spots for tents, and no privy.  Happy Four Shelter is a bare-bones structure a bit farther up the main trail.

Olympus Guard Station was locked up tight.  There's a shelter nearby, a privy, and plenty of tent sites in the surrounding meadows.  This would be another nice place to stay. 

I reached Lewis Meadow at 4 p.m., 7 hours after leaving the trailhead.  It was a very nice place:  plenty of room, privy, bear wire.  The only negative is that it was a long trek to get water:  down a trail to the gravel bar, then a long ways across the cobbles to the active river channel.  During higher-flow season, the river channel is probably closer.  There were a few other parties camped there Monday night, but it didn't feel crowded because there was room to spread out.

Day 2:  Lewis Meadow to Blue Glacier and return.  15 miles.  The day dawned clear.  With 4200 feet of elevation gain, this was a long day, but doing it with a light pack helped.  I left Lewis Meadow at 7 a.m. and reached the top of the lateral moraine overlooking Blue Glacier at 1 p.m.  About 1.5 miles past Lewis Meadow I encountered the only big blowdown on the entire hike. I saw no other hikers for the first few hours, until reaching Elk Lake Camp, where I saw one.  There's a nice shelter at Elk Lake Camp, with 4 bunks.  The camp is well above the lake, which is only partly visible through the trees, and the trail doesn't pass near the lake.  

The big washout just below Glacier Meadows Camp wasn't much of an issue.  A new cable ladder has been installed there, and getting down it was just a matter of hanging onto the rope, facing into the slope, and carefully stepping down the rungs of the ladder.  The only real challenge was getting ahold of the rope at the top, which required taking a few steps out onto a loose scree slope.

I'd been picturing Glacier Meadows Camp as sitting at the edge of a meadow, with a view of the Blue Glacier.  This is not the case.  The camp is in the forest, and no glacier is in sight.  There are a couple of small but sturdy shelters there, and a privy.  To find the big view, you have to climb another thousand feet over another mile.  After climbing a couple hundred feet above the camp, the trail emerges into a small, steep meadow, where the fall colors on the Sitka mountain-ash and huckleberry bushes were lovely.  Above the meadow, the trail climbs steeply through talus, until you finally crest the lateral moraine and the view of Mt. Olympus and the Blue Glacier just smacks you in the face.  The glacier was not, in fact, blue, but the sky was, and the scene was spectacular.

The descent to Lewis Meadow took four hours.  On the way, I passed about a dozen backpackers headed up, including two with ropes and ice axes, aiming for the summit of Mt. Olympus.  I reached my camp at 5 p.m.

Day 3:  Lewis Meadow to trailhead.  11 miles.  I packed up camp in a light drizzle, making me feel fortunate that I'd had clear weather for the previous day's climb.  The walk out took about 5 hours.  Once I passed Five Mile Island, I encountered many day hikers, which became a steady stream as I approached the trailhead.

did a 3 night, 4 day hike in and out to see the Blue Glacier this week. Overall, beautiful trekk, with lots of sites to be had. Trip went as follows:
Day 1: 5 miles: Hiked into 5 mile island. stayed close to the water where i can refill my pack before i left. the trail from the TH to 5 Mile was pretty clear. There are a cpuple.of ups and downs in terms of elevation, but nothing serious. Great spot for camping, I thought. Though you are required to have a bear can if you stay here.
Day 2: 5 miles:Hiked to Lewis Meadows to camp. Ran i to two river crossing where tou can option to cross a log jam or later, one big fallen tree. Didnt have to get wet. Lewis Meadows was a popular spot, abd the first stop for many before advancing up the mountain closer to the glaciers. I preferred 5 Mile more, but there were many deer poking about eating the green off the bushes. I also didnt find another water source besides the Hoh. The the silt didnt seem to bother my Sawyer filter, so it might be alright for other filters.
Day 3: 15 miles: Day hiked from Lewis Meadows to see the Blue Glacier, and I will say. the glacier was BEAUTIFUL! the entire trekk took me 10.5 hours, so I would recommend starting early if you plan on day hiking from Lewis or OGS. You.may have to do some rock hopping at Martin Creek to pass the creek. This is also a great source of water before moving on. The latter is a bit more frightening and challenging than I realized, but still maneagable. its quite popular, even during the week, so I really felt comfortable knowing other fellow hikers could spot me should something happen. Be sure to bring gloves or use the communal gloves at the bottom or top of the latter. The climb to the lateral moraine from Glacier Meadows was stated at .9 miles. Just know that that thats a direct elevation gain., scrambling up plenty of rock. Climbing up the rocks, it may not look like a path, but its thrre. The view was all worth it. Leaving a gorgeous glacier up top Mt. Olympus. Scurrying back down and to the latter, the rungs are certainly far between, and Im 5'5". Reaching eachnone took a 90° angle on my knee each time to push off.
Day4: Packed out of Lewis Meadows, back down to the trailhead.

Did this as a 3 day/2 night backpacking trip. Most important thing to note: NO BUGS!! There were a few mosquitoes at night, but as someone who searches far and wide to find trips without swarms of bugs, this was the ultimate winner. 

We stayed at Lewis Meadows both nights. This made the milage pretty long each day, but luckily the trail hardly gains any elevation from the TH to this camping area. We took the advice of 2 exiting backpackers and kept walking all the way to the river to find a site. While there are plenty in the meadow and forest, we found a prime site right on the bank of the river itself!

Going from Lewis Meadow to Blue Glacier and back on Day 2 makes for about 16 miles round trip with quite a bit of elevation gain. My legs were definitely sore by the end of the day, but hiking with only a day pack helped. A huge THANK YOU to WTA for replacing that ladder! We had no troubles going down and up, and felt pampered by the pairs of gloves stashed there to make the climb even more comfortable. 

Overall: NO bugs, a very well maintained trail (there's a couple rivers that you must navigate by log-hopping, but all were easy to cross), and a great campsite. The entire area is beautiful, and we thoroughly enjoyed each section of the trip. Mileage each day is roughly estimated below:

Day 1: TH --> Lewis Meadows: 10.3 miles

Day 2: Lewis Meadows --> Blue Glacier --> Lewis Meadows: ~16 miles

Day 3: Lewis Meadows --> TH: 10.3 miles

What a spectacular place!!

I tackled Blue Glacier as a 3-day/2-night solo backpacking trip. I spent both nights at Martin Creek Campsite located 14.8 miles into the trail. It made for a long first/last day, but I really liked the site and the ambiance of the creek, so no complaints. Some things worth sharing:

• The Ladder: The NPS replaced the damaged ladder this weekend just before Glacier Meadows (at about 17 miles into the trail) - see the photo of the new ladder below!. The ladder also has a rope installed with it to give you something to hold on to as you ascend/descend. I brought a pair of work gloves with me to use for the ladder. I wouldn't say they were absolutely necessary, but I was glad I had them for extra grip. There were also a few pairs of gloves at the bottom at the top that folks have left behind for use. 
• Bugs: Really none to speak of for most of the trail. At Martin Creek, I did find a few interested mosquitos after sitting still for quite awhile, but not too bad at all.
• Trail Condition: The NPS crew who worked on the ladder also spent some time repairing a few parts of the trail around Martin Creek. Trail is in really great condition and very easy to follow. Note that the sign at the fork in the trail leading you to the Lateral Moraine or the Terminal Moraine viewpoints is on the ground hidden in a bush, so look down if you're not sure which path to take. There were very few people on the trail when I was there - I had the entire Lateral Moraine viewpoint to myself for 3 hours mid-day on August 9th. 
• Elevation Gain: Note that the elevation gain WTA lists here is not really accurate since it's just looking at the elevation delta between the trailhead and Glacier Meadows. If you count the ups-and-downs in-between, and the additional 900' elevation gain to the Lateral Moraine viewpoint, the 6000 feet of total elevation gain that AllTrails lists is more accurate for the ~37 mile trek. 
• Wildlife: I had a herd of about 50 elk cross in front of me about 8 miles into the trail. I also saw a few deer near Olympus Guard Station camp. No bear sightings, but did see plenty of slugs and quite a few frogs.

Thanks to those who worked to fix the ladder the day before I showed up - felt like I had a red carpet laid out for me :)

We did this as a 4 day/3 night backpack trip. The weather was beautiful but hot and humid! The first day we hiked to Lewis Meadow. Day 2, we got up early and backpacked to Elk Lake. We set up our tent and used day packs to hike up to Glacier Meadows. The rope ladder is sketchy and steeper than I thought. Lots of people do it with full backpacks. I heard from several backpackers that the park service is going to work on the ladder this week or next week. They were not working on it when I was there. Day 3, we hiked back down to Olympus Guard Station. Day 4, we hiked out. This was a good schedule for me as I am not the fastest hiker. Lots of people complete this hike in 3 days. Just remember to add in time at arriving/parking into your first day. We had to wait an hour to get into the park and we arrived around 10:00 a.m. on a Monday. Beautiful way to spend 4 days!