I'm still in school so I have to transport books and my laptop daily. I went with this backpack, it's great quality and it keeps my laptop protected with its own internally padded pocket.
http://www.thenorthface.com/catalog/...s/heckler.html

 

I'm sure that's a nice bag but I want somethng the bike can wear - not me. A backpack style would be fine, a convertible one but I'll pass on a regular backpack, I already have a large Camelback one.

 

I use a standard laptop case and made my own tie down straps. I can sit it against my sissy bar when I'm setup of for passengers as well as on my solo luggage rack when I'm setup for solo.