make sure you have enough disk space, only issue could be performance if the host system is loaded.
I guess I should have clarified better initially ....
Disk space is easy to handle and kind of a mute point here, i.e. I recommended they set the VM repeaters up w/ 100GB.
I think the main concern is network IO on the virtual switch and what impact it might have on other VMs on same host? If our repeater has the potential to impact ESX host and other guest VMs with heavy network IO is that something that can be managed by ESX's cool HA, DR, Vmotion, etc.. features??
it would be like putting a file server in a vm, or running wsus or yum repo from a vm. it depends how much they are pushing out.