[ILUG] Dilemma with open-source VOIP systems

[Denis Hennessy]

Does anybody have experience with running a linux-based voip/pabx 
system?  We're split across several offices internationally so it seems 
to me that we could get big savings using our net links to carry voice 
as well. The Asterisk (www.asterisk.org) PBX seems very good but none of 
the local suppliers seem to favour anything other than cisco. They're 
also proposing all kinds of infrastructure upgrades (MPLS-capable 
switches and routers to improve QoS) which I'm not completely convinced 
I need.

I'd really like to hear from anyone that has tried an open-source route:

    * How did it work? Users happy?
    * Who did you get to install/support it?
    * Did you need to upgrade your IP infrastructure?

Thanks,
Denis