I think overall, it's a decent mockup, but I have a couple quirks:
1. The battery is going to take up a whole side-- either the front or back-- of the computer. I think it's going to be the front, because if it were the back, all the ports would have to be shifted forward, and Apple wouldn't want to do that. But if the battery's on the front, that means the optical drive couldn't be on the front, and would have to be on the side.
2. WHY does everyone love the MacBook Air's keyboard? When Jobs opened the Air for the very first time on stage, I saw the keyboard and thought it was revolting. I'm really kinda hoping they'll use the same keys on the current MacBook Pro. I also think they're easier to type on than MacBook keys.
3. I want another firewire 800 port!!!