I have been using one of these in my home office now for over 6 months. In that time I have found it to be a very useful piece of kit.
The sound quality is good and the controls well laid out and easy to understand. In a typical working day I use this phone for 3-6 hours, mostly on conference calls.
The phone sits next to me on my desk, maybe a couple of feet from where my head is and usually picks up my voice just fine. On a very few occasions people have had trouble hearing me, but if all else fails I can pick up the handset. I've probably done this only 2 or 3 times since buying the phone. I also bought a headset with the phone, but have only really used this to test that it actually works.
A big selling point for me was the ability to plug in 2 phone lines, so I can also answer or dial out on the home land line from my office without needing a separate handset.
The phone also has a rear microphone for use when more people are present. I have never used it in this sort of situation so I can't say how well it works.
As another reviewer has said, this phone does not support UK caller line ID. I would agree that this is its biggest drawback, although in practice I have not found it to be a big issue because I mainly use it to dial in to audio conference bridges and give out my mobile number for incoming calls.
It is also a very good looking phone.
Overall, I've given it four stars because it does the job I want it to do very well. If Polycom would support UK CLI, then I'd probably give it 5 stars.