Did you guys check the new PearPC JIT version (0.3.0) ? It's 10+ times faster and is adding Altivec compatibility shortly (meaning even more speed).
According to the authors, much more is planned in the future to enhance the overall emulation pace.
I just installed MacOSX 10.3 (Panther) onto XP Pro and it really rocks!
And my PC is a rather modest mobile (P4 1,8 GHz, 512MB, ATI Radeon 7500).