The 35W and 45W i5 and i7 models seem quite good. There isn't too much data on the internet, but they seemed to offer >90% gaming performance of a standard chip, with that crazy low tdp.
The only problem I've seen with the 35w chips is their availability. They are sometimes hard to find a place to buy them, and sometimes are marked up considerably because of this. But otherwise, clock for clock, they are very competitive with the full power chips like rawrr said.
I think Anandtech did a review of the 35w versions vs the standard power versions.