Nothing too much performance-wise. The new plastic one is even, at least in name, unibody. But it has a glossy keyboard area which you can scratch up pretty easily with a watch strap (I tried this at the store).

Looks like they put in a new battery in the Pro, and it has a fancier graphics card, SD card reader, and Firewire.

To me, the Al casing is worth a bit more money and wouldn't mind an SD reader, so I'd watch the Apple refurb store for last-gen Pros (which is what I did in January).