I've been using the 'camelback' for about a year now.
It works fine, the 'bite' will need the seal/slit breaking (took me two rides to figure out it wasn't a cap
The On/Off lever can sometimes go a bit too far 'on' and so stop flow. You'll get use to it though.
Unfortunalty, I tore mine near the medium zip, I think I snagged it on a tree. Last week I stood on the belly belt and it's a tad broken.
Still Fit's well, doesn't flap around and holds enough gear and sometmes a jacket once the liquid has been supped a bit.