The tube or bite valve freezing/insulated is NOT so important because you can always blow air back into the tube after you drink to keep it full of air. This is just a matter of habit. The neoprene cover is a pain to shift between bladders if you have more than one and like to really clean yours out in between trips.
The important part is to keep ice out from the bladder because it will 1) chunk up the tube pick-up 2) it will brace the sidewalls of the bladder keeping it from deflating, so that no water comes over the shoulder and you suck air.
In my BD Attack Pack, there's room enough to wrap a fleece cover 'round the bladder, and to shove in a iron oxide heat pack. Basically, find a pack that fits your other needs and a little bit of ingenuity and habit modification can keep you from sucking ice.
Off the shelf, the Stash packs are great, I've borrowed one before, but until this season, they haven't been big enough for all the stuff I seem to wind up hauling (because no one else wants to, the back of my hand to them!)
(Edited to say that I'm fortunate enough to date a fast-skiing seamstress who can make a fleece cover for _ANYTHING_ in about 10 minutes)
[ January 02, 2004, 07:06 AM: Message edited by: comprex ]