With the recent release of VMWare Fusion 2.0, you'd be forgiven for thinking that Parallels was no longer relevant with it's lack of Direct X 9.0x support with Shaders 2.0. and the lack of news of late from the Virtualization software company.
But Parallels is expected to match, if not raise the bar with version 4.0 of its Mac OS X virtualization software.
Parallels 4.0 uses a more optimized virtualization engine than 3.0 which in itself should offer performance increases but the biggest thing is that Parallels 4.0 finally adds Dual Core support which will help improve performance even more possibly allowing it to overtake Fusion in terms of general performance.