If you need a hydration pack that can hold a lot of water.. this is what your looking for. 3 liters is A LOT of water. For me this is exactly what I wanted. I just use it to ride my road bike. And where I live it gets stupid hot in the summer and I never had enough water.. now I do. The single pocket is big enough for my cell phone and ID.. probably wont fit to much else in there. But if you really have to you could probably stick some stuff in with the water bladder.
Only complaints I have is that I wish it had the velcro hose holder on both shoulder straps instead of just the right. I have to look over my right shoulder for cars and would rather have the hose on the other side. Would be nice to have a way to secure the excess straps to keep them from flapping in the wind.