The one thing I really want from a camera backpack is fast access to my gear. Not being an open invitation to thieves is a verrrrrry close second.
I have two camera backpacks I absolutely love; one is the F-Stop Kenti, and the other is a European Crumpler model (their ranges for some reason vary massively from continent to continent).
The Crumpler is smaller (sometimes too small, which is why I also have the Kenti) and has no laptop section, but it's well thought-out, with a camera section at the bottom and a daypack part at the top - the camera section is quickly accessible through a side door, which is a must-have for me, whereas the daypack part opens towards the body, which I find extremely reassuring. Plus, it absolutely does not look like a camera bag. The trouble is, they no longer make this marvel of a bag, and haven't replaced it with anything comparable.
The Kenti similarly has a camera section with side doors at the bottom, which fits my 7D, 70-300 L, EF-S 10-22, EF-S 60mm macro, the cheapo nifty fifty plus a few bits and pieces; a 13" laptop pocket; and an expandable daypack section at the top that you can get quite a lot of crap into if necessary. It's not quite as casual as the Crumpler, but it doesn't scream "camera bag" either. I can wholeheartedly recommend it if it's big enough for your gear. (F-Stop will, in my experience, respond quickly and helpfully to "will my gear fit in this bag" questions on their customer service site.)
Before I acquired either of those two bags, I had a close look at the Lowepro Fastpack 350, which was far too bulky for me, and the Tamrac Evolution 8, which I just somehow didn't like much. But that's obviously a matter of taste, personal priorities and the amount and type of gear you have.