Hiked Section I.1 of the PCT (White Pass to Chinook Pass) as a three day/two night backpack. Started at White pass and headed north. The first day was beautiful - dozens of little lakes hidden through the trees just off the trail and almost no major elevation gain. There were a couple of trees across the trail on this day, but only one was any challenge to navigate. Stayed the night at Snow Lake, which was beautiful. The campsite is fairly large, with three distinct spots for fires (allowed in this section of the PCT outside of Mt. Rainier National Park). It's an easy distance to the lake for water as well, and we didn't have any problems with mosquitoes. Someone had left a circular grill grate at the campsite, which we made use of briefly to make pancakes for breakfast.
The second day we headed up to Two Lakes. This was a decent elevation gain day, but it is spread fairly equally across a distance so it never seemed too strenuous, which was a blessing as we were starting to really feel our packs that day! We were glad for a bit of a later start as well as we ended up on the exposed face of the mountain after it had passed into shade. Two Lake is not viewable from the trail above - we were a little concerned that a somewhat marshy/dried out area below was what was left of the lake, but that isn't it. It is a bit of a hike down to the lake for water though so fill up before you get there! We stayed at the campsite right off the PCT, which we shared with three thru-hikers for the evening. There was another couple that stayed down by the lake, where there are even more campsites.
The last day we headed all the way to Chinook Pass. The views really impress on this section of the trail. After a short climb in the morning, Mt. Rainier came into full view, and stayed that way for a good hour and a half of hiking. Dewey Lake is a real jewel, especially when viewed from above! Getting above it requires the first real bit of elevation gain on the trail, but it is short and the views are worth it! Finally came over into the Chinook Pass side and walked over the Mount Rainier National Park bridge over the highway, and down to the parking lot. We parked a car at either end, but were very glad we started on Thursday, as the parking was completely full and overflowing down the road quite a ways in both directions when we came out on Saturday afternoon.
Overall, about ten miles each day resulted in a lovely hike, with great weather. There are a few huckleberries still left on the bushes, and in a week or two they and the vine maples will be in full fall color. Mosquitoes aren't too bad, and will probably continue to get better, and the trail is in fantastic shape. Highly recommend as a first multi-night backpack due to the lack of elevation gain and the pleasure of nice established campsites that allow fire!