General availability will be at the end of October 2009 and MSRP is suggested to be around $199.00 USD.
I've had the opportunity to work with the beta version of the phone (called the "Oak) for the past six months and I'm happy with the overall quality and feature set. Similar to teathering a Tanjay (Polycom cx700) to your PC, your actions on the phone apply to the MOC client and vice versa. For example, if you place a call with the CX300 phone your MOC client will show the call being placed. Basic phone features such as mute are available from the handset as well.
I'm particularly happy with the overall button feel and handset. This is a big step in the right direction for Microsoft and the end users. I forced myself to use the handset for a 2 hour call the other day and didn't have an issue with fatigue.
Considering the price point and feature set, I can't imagine anyone purchasing the CX200 anymore.
If you get your hands on one of these units make sure you upgrade to QFE2 (July 28th patches). I haven't seen these available on Windows Update yet so you can get them manually from here: