Offical team blog for SSDT, a tool for on and off-premise database development
We recently released a new version of the DACFx runtime, DACFx (October 2012). This latest release brings with it several changes that affect compatibility between DACFx and SQL Server Data Tools (SSDT).
DACFX (October 2012) introduces a new package format and support for features available in SQL Server 2012 Service Pack 1. These changes impact compatibility with SSDT resulting in the use of this newer DACFx version to be blocked to avoid compatibility issues customers could experience. This compatibility issue does not impact SQL Server Management Studio (SSMS) or other client tools.
Note: If you have already acquired DACFx (October 2012) to enable scenarios in other Microsoft products which depend on this latest version of DACFx, removing it to repair SSDT will break these scenarios.
First of all, why don't you start using a version scheme, so it is easier to distinquish between versions. It is much more likely, that v1 and v2 are incompatible, than september release and october release are. Also when are you going to use the buildin update mechanism in visual studio 2012? With these frequent releases, it can be a problem to keep developer tools in sync when some update and some doesn't, and there is no easy way for the developers of getting info on updates, except going to this blog.
Agree with Mikael, SSDT, VS2010 and VS2012 with TFS client on the same machine is turning into a full time maintenance job. I'm doing more troubleshooting of my toolset than I am working on fixing bugs in my own code these days.