Without the SSE instructions, the TBird will be lagging quit far behind the P4 in some of the most SSE optimized applications (professional software mostly I think). I wouldn't equate the TBird performance to a P4 in such a general way. But the Palomino, with the SSE support should close the gap significantly where the PR rating may start to make sense (if AMD makes an honest effort to accurately access the relative performance differences). Just my humble opinion.
FWIW, I think AMD will be honest in their PR rating. Their past actions speak well for them. AMD seems like an honest, fair, and upfront company.