If you have any issues with it under VMWare then give me a shout, we specialise in VMWare installations.
However, frankly the software's so small and backs up so well i'd probably not recommend a virtual machine anyway unless you have multiple PBXs required, for the following reasons:
1) The software's not exactly complex to recreate from scratch (other than voicemail) in a pretty quick time.
2) You'd be mad (IT wise) to put it on the same box as any other services anyway due to uptime issues, and hence would theoretically buy your own dedicated box for it.
3) With the churn in voicemail, you're going to have a lot of potential dead filespace in your VM and will need to periodically compact/defrag it.
4) Low latency is obviously high on the requirements list, and sometimes there are minor delays introduced by the presence of multitasking between VMs and VM-related caching issues.
Anyway, as I say, if you still have any issues, just ask.
Cheers,
Mike.