i have a 30 gig video ipod and when i fill it up it kinda lags. so i try not to put more than 25 gigs on it.
i also have a 40 gig creative zen xtra that i've skied with for a while, it was great until about 2 years afer the purchase. if it is sitting vertically, like in a pocket, it will sometimes freeze, then restart and turn off until the battery dies.....i dunno if i took too many crashes with it or what. but it works otherwise, as long as it's sitting on it's back. going 4 years strong now.