I ski w/ a camel back sometimes. I rarely ski park but mostly hike back country. The problem I've had w/ mine is the water freezing. I bought one of those insulated tubes and that helped a little but not much. I have friends who wear theirs under their jackets and they never freeze but then you have all that extra bulk under your jacket.
I got an insulated tube on the pack I bought from EMS and there's a pouch inside my jacket for it, I love it and it doesn't really interfere- You don't realize how much you drink though- I go through 3 bags a day, and I never used to drink anything
I never used to drink water during the day and when I started riding w/ my camel back I would drain the thing in no time. But I also felt better throughout the day, especially if you're hiking alot. Keeping hydrated is KEY
I have a military one, its called the MULE, its like a backpack type one and its got an insulated tube... never been skiing with it, but I guess I'll try it this year... even tho u dont notice it like u do in hot weather, u still need just as much water