Top 8 IP Telephony & Unified Communications Tools
Cisco Unified CommunicationsDigium AsteriskMitel Communications DirectorGenesys PureConnectSiemens OpenScapeDigium SwitchvoxNEC UNIVERGE SphericallMitel Application Suite
It's a solid, robust solution, that has many integrations with third parties.
We use Extension Mobility and Jabber a lot with mobile remote access. In addition to video calls with Jabber, this greatly enriched communications between coworkers.
The most valuable features are call recording, call logging, and the stability.