I started with a backpack on my back. While it didn't feel unnatural, even in cold weather I sweated like a dog. Plus, I couldn't carry much beyond my office stuff. And because it was black, it turned me into a bit of a ninja at night.

Next I tried putting it in a rear basket. It actually felt a little weird not having it on my back; worse, having that much weight on top of the rear rack made the bike wobble. This was the worst.

Finally - this is the best - i got my employer to spring for the Topeak DXP bag with fold-out panniers. they are just large enough for my laptop in a sleeve, and the setup is wonderful. I put my office stuff in one pannier and clothes in the other, lunch in the trunk part. Haven't ever looked back.