The big differences start with Athena that is now 11 speed. Each step drop a little weight, but other than that, you won't notice much of a performance difference. Centaur and Veloce are still 10 speed.

As for the shifters, the internal mechanism on the 10 speed models is largely the same, but the clicks from the right finger lever are much lighter, due to a difference in the detents in the index disc. It's still not clear if this has been changed for 2010, to match the firmer clicks of 11 speed.

The other difference is ball bearings on the main pivot shaft. Record and SR have the ball bearings and Chorus might, but the lower levels have a plastic bushing, despite Campy info to the contrary. I've disassembled 2009 Centaur shifters and verified the plastic bushing.