Yet another bit of information...
I had to re-install Ubuntu yesterday (long story) and I reinstalled VMware as well. After the re-install, I actually had VMware running very well for one session. Here's what I did differently:
1). I used the latest ATI fglrx drivers - 8.18.8. I had been using 8.18.6 up until this point.
2). Switch the CPU Freqency Governor from "userspace" to "performance". This set the CPU at 2GHz.
3). I used EXT3 for my file systems instead of XFS or Reiser.
4). I pre-allocated the VM hard drive space. Before I had it configured to grow as needed.
For the first session, immediately after installing the VMware tools in XP Pro, everything was fine. I thought I was on a different machine.
That's the good news.
The bad news is that I left the machine running Windows Updates and walked downtown to get lunch. When I can back the machine was locked. I couldn't use the keyboard, the mouse moved, but the system would not respond to "clicks". So I hit the power button, killing Ubuntu.
When I restarted, the performance was in the gutter again. Nothing I do now is any better than before the re-install.
I've also noticed that the VMWare tools icon in the XP systray takes a *very* long time to go from "not ready" to "ready".
Don't know if it helps or just muddies the water, but there it is.