I used to have a 17" PowerBook (first 17" model), and I carried it around a lot. There's a Halliburton case that fits it snugly on all sides; no rattling or anything.
People complain about the weight and size, but I never noticed a problem. Of course, I'm a pretty big guy.
Actually, yes. I have a Incase laptop sleeve, and it fits in my backpack perfectly. It's usually the lightest thing in there, too -- at least, my shoulders are happy when I get to leave the books at home.