If you haven't grabbed the leaked Windows Mobile 6 upgrade already, keep your pants held up until May 4. We just got a tip from our T-Mobile source that the official release will be this Friday.
The caveats are that WM6 doesn't have the "My E-Mail" client, and all your data on your phone will be erased. Once you upgrade, you'll get some error messages from "701" unless you log on to My T-Mobile and delete your "My E-Mail" accounts. Other than that, you can bask in the fact that you're the first in the US to have WM6 phones.