I really like it, You can make it very small or very large depending on how much stuff you pack in it because there are straps to cinch up empty space. I have loaded it up pretty good a few times and honestly I really don't notice it when I am riding due to the way that it sits on your back. When I do short rides after work I don't put much water in it unless it's really hot and humid.

I bought one for my wife too and she loves it.