For a lot of us, that would be next Friday.

At some point - most likely after noon PST - version 0.9 of the API will be replaced with the final 1.0 release.

There are no expected interface changes between now and 1.0.
There has been one change in the 0.9 timeframe.

This question will be updated once the transition has occurred.

Version 1.0 of the API is here, officially, as of ~1:30 PM PST. Enjoy.