We are currently running on SW + PDM 2011 SP5.
We have noticed that the first service pack often contains bug that are fixed in later SP.
So as a general rule we wait until SP 4 or 5 are released before we do any upgrading. For any earlier SP you have to test everything including installation and distribution on a separate server before implementing it to the working environment.
Does 2012 fix this problem. If youare in Solidworks and use the File Open command within Solidworks to browse to an assembly in the vault that you do not have the latest version of the files, and you then opent that assembly, EPDM does NOT pull the latest version of the files for you even if you have the "get latest version" switch on. This is frustrating in that you cannot trust what you are seeing without looking at the versions loaded.