Ultimately, as in many forms of technical climbing, it can often come down to "can we do this without falling". Crappy steep snow can be nearly as bad as verglas in my opinion, as it can lure you into a false sense of security one second....then turn into hell the next. It can ultimately come down to a calculated risk on the way up, and survival on the way down. Exercise good judgement and if your party is feeling shaky and the snow sucks, maybe have an alternate plan.

They are made mostly in my country for the odd bit of soft snow going up but mainly for coming down the glacier in the afternoons. They are really good for abseiling over scrunds with and placing one while the other person crosses a crevasse, and of course for crevasse rescue.

In the Sierra Nevada you would have to be pretty keen to take them. But for learning perposes (if you had plans of climbing something with a bit more grunt) go out find an aspect and a nice 40 or 50 degree slope and go nuts. I would recommend practicing crevasse rescue at least 50 times with them using all the different anchor types and situations that you can think of. They are much much more difficult than they seem come crunch time. 40m of 8mm probably won't get you out of a crevasse and there are a few on Shasta. I have been up their and seen them myself. I say that because the rope is to thin for any realistic prussic system.

They have probably already told you all this, so I will head on my weary way.

Have fun on your climb, catch ya.