Continuing that trend of providing the best customer experience on Windows Phone, Nokia has put up a page where regular users can check to see if Windows Phone 8773 aka "Tango" has been released yet, or even just the status of the update.
Located at www.nokia.com/global/support/software-update/lumia/software-update-for-nokia-lumia/ uses can select which region they are in and the drill down to their carrier or Lumia version number.
Interestingly enough, the AT&T Lumia 900 is not even on the list for North America which strongly implies that the carrier is skipping the update and heading right for Windows Phone 7.8 which will include the few Tango features. We're not sure if that's good or bad as Tango doesn't really bring much more than a few MMS enhancements to the 900 but still, it would have been nice to see it as there is no ETA on 7.8.
For T-Mobile, we just posted that the Tango update for the Lumia 710 should go live tomorrow, June 27th, after a delay of a week. We'll be keeping an eye out for that one.
Edit: Some readers correctly point out that Nokia specifically mentions this update is only for the Lumia 710 and 800, so we shouldn't expect the 900 to be listed. This is partially true but only because non-North America (AT&T, Rogers) Lumia 900s shipped with "Tango" pre-installed already, so they don't need the update. Only AT&T and Rogers (as far as we know) and a handful of smaller countries don't have 8773/Tango pre-installed.
Source: Nokia; Thanks, bilzkh, for the tip