Starting from the trailhead, you get a decent opportunity to warm up your legs with about a half mile of gradual incline before hitting granite cut stairs and switchbacks. There's ample opportunity to ease the burn in your legs after a few short steep uphill, which is nice when you're taking older kids who would otherwise want to stop every half mile or so to rest.
We hiked in late February, the snow was spotty until we reached about 5500 feet altitude. Starting the hike at 0500 in 20 degree weather wasn't bad but once you get up the exposed region .75 miles from the summit, it gets a lot cooler with downslope winds. The ambient temp was 18 at that point and because noticeably colder with the wind. We made fresh prints in the snow from where the trail again meets Chilnualna Falls and at the summit it is BRISK. The views are amazing and worth braving the wind and cold. Parts of the trail where it got icy would have been really nice to have crampons, especially the last .5 mikes to the summit (and a few smaller areas shortly before that). You have to weigh the inconvenience of carrying them with how determined you are to reach the summit, because there are parts that are pretty perilous in just good lugged boots. I did the hike in trail runners (my foot gear of choice for almost all hikes) and was fine since I had a good pair of socks, but for an unseasoned hiker, you may want to stick with something that takes a bit more bite in snow and ice f you plan on doing this in the winter or early spring.
My girlfriend and I backpacked this trail in September 2015. we did two day to Johnson lake. got a late start so we didn't make it to Royal Arch. it is possible to make it to Johnson I. on day. it's about 14 mils. Good fishing and there was still water in most of the streams.
If done in the full distance, as I did, it will be rather strenuous. Lots of inclined switchbacks with little to no river view for about 2/4 of the time. The long haul is worth the climb though. there is about 3 pools to stop at and the tallest has a plethora of holes to swim in. CAUTION!!! These pools that move slower than the rest of the river do have leeches in them. Check your body before you decide to go back down. bring water and walking sticks will help a ton.