[quote=davidcpa]$50 + for a Camelback[/quote]
Brand-name stuf is expensive! This link to REI shows Camelback going for more like $100 and more:
http://www.rei.com/search?query=hydratin&button.x=0&button.y=0 Since most of your money is going for the carrying pack, what I did was just get the bladder and tube and put them in a daypack I already had -- More useful than the hydration pack because I could carry more stuf if desired (I used it mostly for day hikes) -- I also cut a piece of backpacker sleeping foam, folded and sewed it to make an insulated 'pocket' for the bladder to keep it cooler longer.
http://www.platypushydration.com/product_detail.aspx?ProdID=9&CategoryID=2 Actually, I found one on sale at the Visitor's Center of Bryce Canyon Natl Park one year for even less.
Difference between the bladders and bottles is that the former can be hands-free if set up right, but the latter can be squirted to back of mouth for rinsing. Also, if one desires filtered water or energy mix, then the bladder is better than one bottle refilled enroute.
I'm glad this subject emerged -- I needed reminding that my Platypus bladder and hose need cleaning.