! Warning: this post hasn't been updated in over three years and so may contain out of date information.Microsoft’s “worst kept secret” got its predicted airing at TED yesterday. The video of the event is available on the TED website already. Also there is an official webpage for the telescope software. No news yet on when this might be available to the public. However it appears that – despite being a C# app, and thus easy-ish to port to Mono – it will be a Windows-only application.
Update: The beta version is now available to the general public (and very nice it looks too)