Atom 1.0 is a Proposed Standard.
So what does Proposed Standard mean?
A Proposed Standard specification is generally stable, has resolved known design choices, is believed to be well-understood, has received significant community review, and appears to enjoy enough community interest to be considered valuable. However, further experience might result in a change or even retraction of the specification before it advances.
Well, it also means that it will get an RFC number. Woot!
The next stop is "Draft Standard". If you want to know all the gory details they're all detailed in, you guessed it, an RFC. At the very least, you have to give the IETF credit for consistency.