Just a note. I have a camera bag (it's nice enough) that does NOT have a slot for a laptop. I don't currently own a laptop. I am getting one though, which means I have to get a new bag. Was a gift so i'm not out any cash, just something to consider even if you don't have a laptop/tablet/netbook, you might get one some day and that might require a whole new bag. Unless you are positive you will never need it/don't mind upgrading/spending later if you ever do, I wouldn't get one without a well padded laptop sleeve.
To add to this, even if you don't have a laptop and don't intend on traveling with one, the laptop sleeve/area is great for holding documentation, magazines and the like. This is the way I travel with backpacks, and I couldn't live without the area for holding papers and such.
Also, do you want a backpack that is exclusively for photo gear, or do you want one with a daypack compartment? If it's the latter, I've used several daypack/photo backpacks, and my current favorite is the Tamrac Evolution 8 (http://www.bhphotovideo.com/c/product/682171-REG/Tamrac_578885_5788_Evolution_8_Photo_Laptop.html
), which I took to Scotland and Ireland a month ago. It lets you take out camera gear from the back as well as the sides (note: make sure to close the side zippers when you're done taking out gear. Thankfully, lenses with red rings bounce [or at least have so far]).
Hope this helps.