I don't konw if there's such a thing as a business backpack. I had a Targus bag for a while, but it eventually lost it's shape and felt sloppy. I switched to a Patagonia Crosstown. It doesn't have as many compartments, but feels much nicer. It is a little tight around my 14" laptop.
If anything, I recommned you try out the laptop slip first before buying. I think the side-entry pockets are probably the fastest in the airport. http://store.apple.com/us/product/TW...S-SHOP-Froogle