Emetrotel with the UCx product is definitely the way to go in my book. If you bleed Nortel blue, you should definitely check this system out.
You can use everything from Nortel Unistim phones to any manufacturer of SIP phones on this system. I have one set up for my small telecom business and I have Nortel: 6 11xx Unistim phones, 2 11xx SIP phones, 1 Meridian M7208, and 1 T7316, 1 i2050 working on my laptop set all working on this system. I also have 1 Cisco 7970 and 1 Avaya 9630 SIP set working on the system as well. I also have 6 remote users on the system spread out throughout the USA and one person in Prague. The remote user feature is quite simple......set up an external IP address on the system and simply connect any Unistim phone and have a good network, and you are set. Its usually as simple as plugging a Unistim set in and the phone comes up.
Licensing is quite simple. You can start out with a 5 license system for half the cost of a BCM, and that includes all the features and functionality Unified Messaging, Call Recording, Conferencing, IVR, Find-me/Follow-me mobility, Unistim/SIP phones, Paging, Park, Transfer, Music on Hold, Enhanced CLID, Personalized button labeling, and Nortel CS1000/BCM fashioned features.
One thing I find quite fascinating about the UCx is the fact that the system acts as hybrid between a traditional Nortel Key (Norstar/BCM) and PBX (Meridian 1/CS1000) system. One frustrating thing I felt about Nortel in the past was that the Norstar/BCM systems acted independently from the PBX Meridian 1/CS1000 sets. The UCx works like a CS1000 no matter if its a 5 user system or 5000 user system.
The system is designed by Nortel alumni who used to work in everything from CS1000 to BCM/Norstar to Networking with Bay Networks.
I definitely recommend this system for a high end, low cost IP PBX solution that actually allows you to use digital Nortel phones as well!
Joe