I have the leather version of this:

http://www.briggs-riley.com/travel/@...erbackpack.asp

(sorry cannot find a link to the leather version).

Very comfortable to wear, and does not mess up a suit. I do a lot of business in Japan where you spend a lot of time on the trains or walking between meetings, and a backpack is very convienient vs. a regular computer bag (your shoulder gets tired after a while), or a rollaround (more difficult to navigate up and down stairs, over bumps, etc.).

I paid the extra dollars and got the leather version, because it looks a lot more professional to bring a nice leather backpack into a business meeting rather than a cloth one.