Late last night Microsoft released the statement that many IT professional, directors, and CIOs have been waiting nearly a year to hear: the slated public release of Lync Server 2010.  As the Release To Manufacturing (RTM) milestone has been reached this means that all code changes are completely locked, the interfaces of the client and server applications are final, and only the documentation may still receive some polishing. But between now and the General Availability (GA) date of November 17th it will be just hurry-up-and-wait while the world counts the days, minutes, and seconds for that download link to appear in TechNet and MSDN subscribers listings.

I noticed there were some immediate questions on the official announcement around what RTM/GA meant, what upgrades paths were available, and what coexistence scenarios are supported.  Here is the same response I posted in the comments to address those questions:

"There is no supported upgrade path from RC to RTM as the Release Candidate documentation stated that it should only be deployed in test labs and not into a production forest. Only organizations involved in TAP/RDP early-adopter programs with Microsoft were assisted with in-place upgrades from build-to-build.

Also no Schema changes were reported between RC/RTM but until the code (or an official statement) is released there is the possibility that something was changed.

Additionally the public release (GA) of the software itself is slated for Nov 17 as Kirk stated in this article, RTM is an internal-only product release and signifies that the code itself is 100% locked and finalized.

Full documentation will likely be released and posted to TechNet on the same date, and this will include migration paths and all other documentation not yet available. This covers the coexistence scenarios which do include paths for both OCS 2007 and 2007 R2."