Flight is only for the Windows operating system.
Regardless of the specs they will post, it will require a 256 bit video card with at least 512k memory, and Shader 3.0 along with DirectX 9.0c capability. The CPU will likely need to be a multi-core running at 3.0 GHz or better. There may be memory problems with a Windows 32 bit operating system. A Windows Live! account is needed, and it may require an active internet connection to get the full experience of the game.
I just write this to let everyone know if your computer is a tad old, you may be in for a disappointment with this free flying game. In my case, it would require a new computer to run it well. Some people may be a bit creeped-out at the active connection to Windows Live! Microsoft actually wants a connection to your computer whether gaming or using Office programs. That's where the future is going.
At any rate, as they write, you'll get a flying experience... not necessarily a flight simulator... whatever that means. It could be a lot of fun, but perhaps not what traditional simmers expect.
As of yet, there is no word from Microsoft as to an SDK, or what such a developer SDK might include. So... as far as FSDeveloper goes, there isn't much to discuss. Other forums, such as AVSIM or FlightSim might be more appropriate/responsive places for Flight discussions, until such time as there is some need for 3rd party developer discussions.
Dick