I switched our office telephone system to SIP-based VOIP a few weeks ago and I doubt we’ll ever look back. The office and data center are now connected with one touch dialing, and I just put a Cisco phone in my home on the same system. It’s all seamless. We could have data centers around the world (and I hope we do one day) all on this system.
At the office and data center, I went with Polycom 670s. Polycom touts its HD Voice technology and rightly so. They’re easily the best-sounding phones I’ve ever heard.

At home, just to try something different, I got a Cisco SPA525G. It has a nicer display than the Polycoms, but the voice quality isn’t quite as good. It’s still totally usable, though. It’s also nice how well the Polycoms and Ciscos both work together on the same SIP Virtual PBX.

I even configured one line on the customer service phone to answer our Skype calls using their new SIP feature, although I may not bother leaving that up as very few people call us on Skype and our Skype phone works just fine for that.
The great thing about a system like this for a distributed company like ours is that it makes everyone feel a bit closer to each other. I just touch one button to talk to the office or the data center, and they do the same to talk to me or each other.
Improved, easier and higher quality communications can’t help but improve any organization.