Re:My experience (Score 1)

AccessLine, has an excellent solution in this space. http://www.accessline.com/ They can easily integrate with existing PBX infrastructure, and also bring in new lines with an analog gateway. They do G.711, and G.729b. They provide conferencing, one number service, follow me, faxes, and a interoffice virtual private network (basically your own private phone number scheme). etc etc. They provide all the hardware, and a gui to let your IT guy assign phone numbers to phones.. It's pretty slick.