A piece of closed cell foam sleeping pad makes a great place to sit. I've even seen people cut a small piece, and attach it like a flap on the bottom of their pack, so when they sit, it's under their butt. It just hangs there when hiking. A pad is good for glissading... which is fun, but, better have an ice axe to self arrest if you get going too fast.

Those closed cell foam pads are also handy if you need to splint an arm or leg. Oh yeah, you can even sleep on them. I think some kind of pad is a must in winter, you really need some insulation under the sleeping bag or it's going to be a cooooold night.