Less dust
They've also released an IS version of their cracking 70-200mm f4, which has been a customer request for as long as I can remember... (I've got the non-IS version of this lens, and it's a nice bit of kit)
Alas, I can't really justify trading up just yet, but it's good to see they're listening to us. Next stop, an ISO-readout in the viewfinder please!