VMware 2.0 is supposed to see a performance increase on Nehalem due to changes in some type of paging table in the hardware. I can't seem to locate the thread post now. I was using Parallels and switched to VMware when I got the new MP, so I have no frame of reference.
I am running a Windows 2003 Server vm w 4 virtual processors and 4 gb of ram. Very responsive and nice.