We use (and sell, setup, maintain) 3Com NBX systems. I like them very much, although they are not entirely my forte in our business. Simple to use PoE phones, find-me, follow-me works well, easy remote administration, robust VM that emails you VMs, very reliable and well-made hardware, relatively easy to add/suport remote users. Things I don't like are 3com support is pretty crappy (read: somewhere in Asia) and we have some problems with analog cards locking up ports a bit more often than I'd like, but I think it's because of our buildings' phone system. All of our clients are running on T1s/PRIs with analog backup lines, with no reported similar problems.
Which reminds me, I gotta bug my boss to send me to training.