Marc has the scoop, but here’s the ultra-quick gist:

  • Beta 1: Late July
  • Beta 2: November

Marc says beta 2′ll be more interesting:

Beta 1 will not contain any of the UI goodies I and so many others are excited about seeing. This first beta is aimed squarely at the developer community to begin familiarizing themselves with the new OS platform.

Expect serious backlash (again) after beta 1, as people continue to look for GUI enhancements over anything else. Hopefully hardcore developers will be able to dig deep enough into this/next month’s beta to allow them to have launch-ready applications, and to give solid feedback on where Microsoft has gone wrong with this release.