I just installed FreeBSD 6.1-BETA2 in VMware Workstation 5.5.1 build-19175. I have not seen the same sorts of timing problems shown by FreeBSD 6.0 RELEASE inside the VMs I use and have created for the Sguil project. I did not see any obvious changes that would account for the better behavior. I hope FreeBSD 6.1 RELEASE behaves just as well.
I am not sure if I will create a Sguil VM for FreeBSD 6.1 and Sguil 0.6.1, or if I will wait for a newer version of Sguil. The latest Sguil version mostly contains client-side improvements. The next version of Sguil (release date unknown) will probably integrate the Passive Asset Detection System, so I would want to include that.