I had the Novara REI backpack, and it is one of the few items ever returned to REI. The main strap started tearing from the bag at the top. Bought it specifically to carry a laptop. Not since replaced with another backpack, because there is rarely a need to transport a laptop, so I'm unable suggest a better one.

For heavywieght items, you may want a stronger backpack. But then you need to consider whether to carry all that weight on your back, or go to rack and bag. Maybe a combo of the two would work best. The jarring and bumps could potentially damage a computer in a bag on a rack, at least on my route, so the back is the preferred location to transport.