A CTP of the Windows Azure SDK should be available shortly. In the mean time, you can get busy with the “Oslo” SDK that has been released already. Downloadable from the new “Oslo” Developer Center on MSDN.
Of course as a Microsoft employee I am biased about this new, but oh so familiar, platform. So don’t take my opinion, but that of Robert W. Anderson. He writes about Windows Azure:
It is the openness of this platform, the ability of developers to mix and match the different components, and to do it between the cloud and in-premises solutions that makes this such a winner.
This last point is an important one. Microsoft is in a unique position to help enterprise IT bridge to the cloud. While I don’t think Amazon and Google will cede that market to Microsoft, their current offerings aren’t a natural fit.
Taking this all together — not forgetting Microsoft’s leading developer productivity story — it looks like a home run to me.