I'm currently considering the following for a 80 person, three office firm - offices are 50 users in office A, 20 in office B, and 10 in office C
NEC NEAX2000 IPS Platform in office A, NEC ELITE IPK for office B, and NEC ELITE IPK Basic for office C - VoIP cards in the switches.
Nortel BCM 400 in Office A, BCM 200 in B and C
Intertel - so much literature I'm not even sure what they're offering any more
Sprint Coral -
Right now I'm leaning towards the NEC system or the Sprint Coral System, but I'm looking for scalability, and most importantly - open standards - compatibility, and overall value -