68% more performance for 50% more cores is still a wicked improvement. Even linear scaling is tough, let alone managing to use a similar system more efficiently with all those cores to bog down memory/HDD/intercore connections.
@joeman42: There is one good reason why both AMD and Intel launches the business chips first. They can ask a lot more for their Opterons and Xeons. Expect it to take from 3 to 6 months, after the business optimized are launched, for the fabs to be ready for a desktop release.