For me, backpacks are pretty much the only way to go when I'm lugging my laptop around. I walk a lot. And much as I might like the look of a chic, slim shoulder-strap case, I invariably start lurching over to the side after 15 minutes or so. Some bags don't fit enough extra stuff in them, and some are too bulky; this one is just right. I like the file separators build in to the main compartment; they're handy for keeping paperbacks and magazines from getting mushed. 

1. The CoDi MaxPak has lots of other handily-sized pockets for whatever you might need to carry; one is long enough for foldup umbrellas or a bottle of water; others fit cell phones, PDAs, or (embarrassingly essential for this commuter) the Nintendo DS.  There's even a little top-loading pocket for your music player.

As for comfort, the MaxPak is terrific, with its padded back and nice, wide shoulder straps. And it's made of ballistic nylon, very tough, weatherproof material. It weighs a little over 3 pounds, empty.  You can buy it directly from CoDi's Web site for $119.