This line of devices has been designed to work with Office Communication Server 2007. I am currently using a model similar to the CX200.
At first look you notice that it lacks a numeric pad, this is because you do your dialing through the Office Communicator Client. "Dial" may not actually be the best word to use since in most cases dialing a contact takes nothing more then a right click so the physical act of dialing is not really there, thus negating the need for a number pad in a majority of scenarios. (image 1) You can click to dial any number that is in your organizations GAL or in your Outlook contacts. If the number or person you want to dial does not meet the prior criteria, you can just type in the number using the Communicator Client to place the call. (image 2)
Other features include:
When I am on the road, I use nothing more then a pair of headphones with a built-in mic. At my office or home office its nice to have a handset to pickup or take advantage of the speakerphone. In the words of one of my colleague's. "there is something old school about having a physical device." It's interesting to think we could be at a point where a desk phone could be considered old school. To me it shows how the workforce is being able to become truly mobile and being less and less tied to a desk or any physical location.