We have OCS 2007 R1 with Communicator 2007 R1 clients. Everything worked fine until I upgraded us to Exchange 2010, and I now get Integration errors where Communicator can't connect to the Exchange EWS site properly to get OOO and calendar data. I spent a lot of time trying to figure that one out, and even after applying the latest update to Communicator and a few other ideas, no dice. In speaking with Microsoft they told me to see if using Communicator 2007 R2 client would help, and it does now work with the R2 client. So this brings up some questions for me.
1. Is it a good idea to update all my clients to Communicator 2007 R2 while I leave my OCS 2007 server at R1? It seems to work fine for me, but I thought I'd ask.
2. If #1 is okay, what is my best option for upgrading all my end user clients from Communicator 2007 R1 to R2?