I've been told that under VMware there are two things you need to pay special attention to:
1) You need to install VMware Tools, and apparently as part of that installation process you install a new network card driver that makes a big difference.
2) There is a CPU timing fix that you need to make to a Grub configuration file.
There should be instructions somewhere on the Web, and if you make sure those two things are done, I understand it makes a huge difference.