Lori: I agree - I carry a Nalgene bottle and a Dromlite bladder. I keep the bottle full, and use the bladder for extra water if there's a dry stretch or I want to make a dry camp.

I've tried, over the years, to move away from a Nalgene bottle to something lighter (bladders, Platypus, Nalgene Cantene, or what have you) but I've always felt "vulnerable" without my trusty bottle. I've finally given up, and carry it on all my trips without a second thought. I know there's nothing rational about it (never had a bladder leak or rupture), but it's definitely peace of mind.