Just get a smaller laptop, or use the cloud or portable media, is all off-target in my opinion. It may be feasible for some uses, but sometimes it does need to be 17", plus as much processing power as you can get, and access outside of the firewall including a USB is forbidden. It's not always an option, so secure, convenient transportation is a pretty good question.

As it is, I either slip mine into a regular padded backpack or strap the laptop case onto my rack, which aren't very happy solutions. I simply don't do it very often. With some nice solid solution that I could clip on or off in seconds, and not worry about during the commute it would be a different story.