Oy.
A Beta and a Release Candidate aren't really the same thing. A beta (in modern times) is a demo. It may or may not have everything enabled, and is mostly just there for debugging and what not. No matter how the beta performs, there will be tweaks and recompiling before the Release Candidate.
A Release Candidate is potentially the final version. It is a candidate for public release that is being tested for errors. That is not to say that all RCs become the final version (this is RC2 for example), just that it may become the final version.
While ATI/AMD's lack of foresight amuses me, this is indeed a new driver. Well, a Release Candidate for a new driver. If no major bugs are found in the next week or two, this will be the public release. Otherwise, a new RC comes out, and another week or two of testing is done.