Some of you may know that Microsoft had announced that the beta version of MDX 2.0 would expired on the first days of October 2006. As promised, it did. What is more, the beta has been removed from the latest SDK release.
Consequences? Either you go back to MDX 1.1 or move forward to XNA-supportive implementation.
Even though it has been clarified that XNA is not officially supported in the above-mentioned SDK, if you use and or ever used MDX 2.0, I believe that moving your programs to XNA is the right path to go -unless of course you cannot wait for its final release, given the features XNA currently offers as well as the upcoming ones.
So go ahead! Support XNA and please avoid the temptation of modifying the date in your system's clock to September 2006 ... ;)