I've been using a Tom Bihn Empire Builder for a few months now, and pretty much love it. It's kinda pricey, but not too bad compared to comparable pieces of gear. Before that, I was using a Tom Bihn Monolith that slipped into my backpack. All his stuff offers excellent protection for you laptop. The Empire Builder has lots of room, and comes with 3 dividers that keep your papers organized and prevent them from getting squished or otherwise mangled while loose in your briefcase. The Absolute shoulder strap is comfortable and very sturdy.
My wife uses the Tom Bihn ID case for her iBook, and while it is an excellent case as well, there isn't quite as much room left over for papers and such after the laptop insert is put in.