The latest Beta is fairly stable, and they have the updated Serial Number in the first post on the forum listed at Daz.  To Get it you reset your download for Carrara 8 Pro will put the downloads available.  Just install the Beta to a different location, you can copy content from the exisiting pro to the new one.  There are several posts in the thread about that, that way you can have both the 8.0 release and the latest beta installed