I recently upgraded a test server from Lion Server with FM Pro Advanced Server 12 to Mountain Lion Server. The upgrade went in the suggested order:
1) update FM Server Advanced 12 to newest version (that supports Mountain Lion)
2) update Lion Server to Mountain Lion
3) updated Mountain Lion to Mountain Lion Server
The install works as I expected EXCEPT for one small gotcha...
A container File set up for interactive content (in my case a PDF) no longer displays in the client. If I switch the container field in the layout to "Optimize for Images" instead, the file displays as expected (without any way to interact, of course).
Has anyone else noticed this? I first thought that it might have been a permissions problem with the files (they are stored on the server), but when I realized that changing the flag for the layout field showed the information, I discounted this possibility.