I have the Tumi bag in ballistic nylon. It's a great bag and very durable. The laptop compartment is in the middle and it holds the computer off the bottom with some elastic webbing (shock absorption). I used it daily for about 18 months when I was traveling every week for work. It still looks brand new. I've even washed it.
I've stuffed it to the gills, carried it on and even checked it. I've dropped it and yanked it around by just one handle.
It's got lots of pockets and is a good bag to keep you organized. The only downside is "no wheels". I used a combination of the handles, the shoulder strap and a collapsable luggage dolly. If I'm just going back and forth the office, wheels aren't a big deal. If I'm flying, wheels are a must. The dolly/bag combo works great and I still use it whenever I travel for business.
I have been considering a backpack style bag for more casual traveling, but I'd like one with wheels. I'll be watching this thread to see what else you find out...