I have the Lowepro Fastpack 250 right now. It's a great bag -- very comfortable on my back, lots of padding, good pockets, straps, etc. My only problem with it is that as my lenses grow (seemingly on their own), the bag is too small ... especially since I have other needs for the top compartment. If I could store lens hoods there and if I wasn't expecting a 70-200/2.8L IS to arrive any day, it'd be perfect.
I guess what I'm saying is that if you don't have huge lenses and you're really using it for camera gear + a laptop, it's a great bag. It kind of bums me out that it's not going to work for me because I really do like it a lot.
PS, I'm switching over to the Urban Disguise 60 because it'll fit the big lenses, my laptop, papers and books for work (I'm a college professor), and more. Unfortunately, I'll have to attach my water bottle with a carabiner.