Zalman,
I decide to try a hydration system after climbing this summer because I had to stop frequently to drink water and while I enjoyed the rest, I thought I would have traveled faster and performed better if I were hydrating more frequently in smaller amounts. I decided on the MSR 2 litere system. 4.5 ounces. It has worked out well. However, on a short climb yesterday I went to a liter Platypus (bottle not hydration system) in my pack and 20 ounce bottle (sports drink) in a "holster" on my waist strap. that system was lighter by 1.5 ounces, and gave me the variety of water and Gaiter aid. I also had a little problem with my hydration system getting icy a week ago, up high, below freezing. I'm going to go to Home Depot and look for a 3/8 inch foam jacket of some kind I can wrap around the tube. The bladder doesn't freeze due, I suppose, to the warmth next to my back.

http://www.rei.com/product/734347