About 4 years ago we upgraded to a Cisco VoIP telephony system. This enabled voice traffic between our sites (and to call local numbers at each site) to traverse our WAN instead of dealing with long distance charges. There has been significant ROI here. We've also deployed MeetingPlace Express, which has helped eliminate a lot of trips between sites, and increased training opportunities.
Cisco is expensive, but their stuff is incredibly well supported, both by them and third parties. Our entire network infrastructure is Cisco, and I'm a fan of the "one throat to choke" approach. Engineers are more worried about solving my problems than blaming someone else.
Even their lowest level of SMARTNet offers next day hardware replacement...
You're correct in that Cisco is expensive up front, but in the big picture (at least for our organization) it's really not a bad deal.