I automated vmware tools install using the open-vm-tools deb (backport to etch). Then used puppet to run vmware-cmd to enable timesync on all of the guests. See here.
This keeps time from falling behind, but we set up some munin graphs and saw time was gaining about 40s a day. so I just wrote another puppet exec to add ‘clock=pit’ to the end of the kernel lines. Newer kernels use time algorithms that try to correct time for lost cycles. Lost cycles are common in virtualized environments. I’ll note how this works out after a week or so.