I have used freepbx/asterisk in a virtual environment with sip trunking and sip phones (even converted old cisco 79xx series) it seems to work in a decent paced environment (@100 users / call center)
We haven't put it into production but I don't really see why it wouldn't work as long as you don't use pri cards. ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
