The new Prescott core is decent at best. It's fast and can definately overclock like a biatch. However, there are a few shortcomings Intel has failed to fix.
1.) No integrated memory controller. This means that the memory controller is in the northbridge and latency is way high.
2.) Lots of pipelines and longer. Prescotts have 31 pipelines that are longer than the Northwood ones, and there's something bad about that. However, since I'm not exactly familiar with what that is, I shall direct any questions to Ownage for awnsering.
Trust me though, more pipelines that are longer are not good for processors.