I actually use either the dromlite 4 ltr or the camelbak antidote 100 oz... either one works really well for me, only complaint I have with the msr is how the drinking tube sticks out off the bladder at the bottom... may be psycological but i am always worried that i will break it off!
Depends on how you're going to use it. I use the heavier dromedary if I'm on a float trip or car camping and not worried about weight and the bladder is being used/carried/filled daily. If I'm carrying it in a pack as a drinking bladder and it's protected I use the dromlite. Its simpler and slides into small places a bit better without the webbing and grommets and crap on it.
You're probably already aware of them, but Sea to Summit make a pac'n'tap, just to throw another in the mix, has slots on each corner to strap it to your pack.