If you try to import a model, and get an error that the model file is from a newer version of Microsoft Dynamics AX and cannot be installed, I have not yet found a way around that. You need to upgrade your AX, find an upgraded AX, or ask for an xpo instead. If anyone has found a better way, I’m happy to listen.
The point is, if you are developing for a customer on a more recent version than the customer has, they WILL have problems. This is, of course, different from xpos in earlier versions. Clearly MS still has some work to do on their “model model.”
EDIT 12 Jul 2012: I requested hotfix 2696835 from Microsoft, which brought the version up to 6.0.1108.403, which was sufficient for my import. Microsoft says, “This fix is not publicly available through the Microsoft website as it has not gone through full Microsoft regression testing.” I imagine, though, that CU3 (just released) would do the trick also.