I've been eyeing up this bag for a while and finally bought it. I'm so glad I did!
I love the bright color but besides the look there's so many great things about this bag. The reservoir is 3 liters and easy to fill up. The bite nozzle is magnetic so it's easy to quickly grab a sip while you are riding and clip it back on all while not missing a beat in your pedaling. The air pocket on the back is awesome. I don't sweat nearly as much as I have with other hydration packs on my back. I barely notice this one is there.
While this pack does fit everything I need for riding, it's a bit tight in there. It fits my spare tube, pump, tools, phone and a couple of energy bars. However one evening it got late and I tried to put my sunglasses in there. It was a tight fit with everything else in it. I'm thinking that the 10 might have provided me the little extra bit of space that I'd like without adding too much bulk.
This bag seems really durable also. I've used it many times and it still looks brand new!