What were you getting on the standard single core test? The reason I ask is I don't think they made any other changes other than making it multithreaded. I get about 9150 on the standard test. Dual core will never get more than 200% in any test using the same proceedure. Given that my max would be 18300 which is less than your 2.9 (says 2.75?) test. The thing is efficiency will never be 100% so the score has to be lower. Honestly unless they made other changes I think the earlier betas might have had some flaw that raise the score slightly.
Thats really not a bad OC there. I generally run 2.72Ghz at 1.48 or 1.5v. My tests at 2.93Ghz require over 1.7 volts and I'd never run that everyday. Probably more the BIOS setting is 113% of 1.55v. To get even 2.8Ghz will probably still require 1.6v.