Open source PBX vs. conventional PBX

My recent how-to article on Trixbox with Exchange UM integration has generated quite a large amount of interest and from what it seems a large part of the IT community is looking/interested in Unified Messaging (this is suggested by keyword searches from Bing and Google).

The question at the back of my mind would be whether or not this is being setup for test/evaluation purpose or full production use i.e. are people using Asterisk (open source)¬†or opting for the more conventional solution from a major vendor like Avaya, Cisco or Nortel (sorry that’s Avaya now!)

No Jitter has put together some interesting key pros and cons on this, but reaches no conclusion.

What PBX do you use?

Source: here