I prefer the Lomo stuff, I have quite a few of their bags (Holdall and the Backpack) and for the money they are fantastic quality. Its a company who make watersports items, so you know it will be waterproof.
I've had the 40L drybag holdall for going on 4 years now, been on loads of trips.. the yellows looking grubby but its still superbly waterproof