I'm glad somebody started this thread. I'm going to REI this weekend, specifically to check out some Camelbaks. My hubby and I might be doing an organized metric century event on June 1st. It would be a first, for both of us. I'm predicting it will be an almost all-day endeavor for us...having never done this kind of distance before. I thought it might be a good idea to wear one of the Camelbak packs that had some storage capacity (I'm thinking along the lines of the women's L.U.X.E. model). It has a 100oz bladder and 500 cubic inches of storage capacity. It would be nice to have the extra room for tools, snacks, storing a light jacket, etc. Am I going to be uncomfortable hauling this thing on my back all day long? Should I be looking at a different model for my specific needs?