Don't be scared by the signs. If you're out of shape, don't attempt this hike, but if you're used to steep trails, don't worry about the alleged cliffs and crevasses--there are none. That's PAST the camp (beyond which you need a permit). Once you leave the Skyline Loop, you're pretty much climbing a steep but not-too-steep snowfield. Spikes are very helpful, but some people in my party didn't use them.
The toilets at Camp Muir--thankfully, they exist--smell worse than any outhouse I've encountered in 50 years. Wow.
Bring something for sliding down on your butt, snow permitting. When I visited in July, there were only a few places where this worked, but it was fun.
We heard and saw lots of avalanches, but they were way across a big gully. If the snowfield below Camp Muir had regular avalanches during hiking season, it wouldn't be open to tourists.