It's the elimination of the plastic macbook, and hopeful price drop on the aluminum one that sounds exciting to me. That's a hell of a lovable (and sellable) machine, the aluminum, but out of a lot of people's price range.
While internal batteries on the 17 wouldn't be my choice, I don't think it's worth getting worked up about for most. An increase in battery life vs. non-removability, no big deal. When I need more than 3 hours, I just bring my power adapter anyway. And the 17 inch? Few are interested in paying so much to lug so much. 15 and 13 are where the vast majority of the money goes, guarenteed.
What I'd like to see is an update to the air. It's so close to being wonderful, but it's just a little too impractical/indulgent to sell well, I think. I'd seen more unibody's by the time they'd been out 3 weeks than I have seen Air's, period.