As of yesterday:
The wait is over. With Visual Studio 11 beta comes .NET Framework v4.5, and the impression I get is that AutoCAD 2012 doesn't really seem to like that. I imagine the official line to be that VS11 will be supported with the next release after Microsoft releases theirs, that is 2014, earliest.
In the meantime the only idea I've got is to change app.config for acad.exe, in want of a finer granularity for versioning, replacing
<supportedRuntime version="v4.0"/>
with
<supportedRuntime version="v2.0.50727"/>
Any suggestions?