Not sure how useful this trip report will be for people, but I figured I'd tack onto a report from a few days ago.
I'm writing this under Umtanum Creek Canyon, but realistically this only shares the parking lot. Once you cross the bridge, double back over the train tracks to the slope to the right hand side when looking from the parking lot. You'll see two narrow dirt trails leading up to the top. These are the route I took.
Going up I followed the track to the right. It's dicey in some places, particularly with how steep it gets at certain points and the footing isn't solid since it's a combination of dirt and loose rocks. Poles are definitely recommended. You'll gain around 800 feet in half a mile. The wind steadily increased as a I ascended; at the top it was doing its best to push me over (my tripod was no match).
I didn't see anybody else at the top. I didn't have much of a goal so I wandered in circles, took a number of pictures, and had some lunch -- you could easily walk for miles back up the canyon, but the wind put a damper on my physical exertion. In any case, I'd definitely recommend going up and taking in the views!
On the way back I took what was the left hand trail of the two. Poles even more recommended on this trail! If I were to do it again, I probably would have gone back out the way I came in (not that it was much better). I slipped a few times and tried to traverse down the grass when possible.
All in all, I only covered a few miles but it was an interesting perspective that most people miss!