Barcelona (AMD's native quad core) is launching toward the end of Q2, but the target is at Server. Claims of 40% gain over Intel platform in certain benchmarks has been widely circulated. (I think it relates to FP performance, traditionally strong in K8). Retail buyers will have to wait till Q3 to get the new Stars processor.

I think all bets are off, until AMD launches Barcelona and we have a good idea of it's performance. Until then, it's all hype. (Intel does hype Core 2 Duo for like 6 months prior to the launch as well..)