This conversation was stirring "deja vu all over again" in my fingers, so I did a bit of searching ... and we had a similar discussion
right here in January when 10.3.2 came out. Here's what I wrote then about the stages of software development; it's similar to d00d's list, but is more lenient of bugs:
In reply to:
Alpha, Beta, Golden Master. Alphas are highly unstable and likely to crash every machine they're installed on, they aren't feature-complete, and they probably don't have anything close to a finished user interface. Betas are much closer to production quality; they MAY crash SOME of the machines they are installed on, they are feature complete by defintion, as the beta stage is used for debugging and optimization, not feature additions. Golden Masters are the debugged betas, where all "do not ship until this is fixed" bugs have been fixed, and the remaining bugs have been prioritized for the next upgrade release. There's no such thing as a bug-free release, only a release free of known crashing bugs.
Once you get the release out the door, you go back to the list of unresolved issues and get working on them for the next release. BTW, if this kind of stuff is interesting to you, you can see the process at work in public on bugzilla.mozilla.org, where bugs are publicly discussed, scheduled, moved, revised, ignored, fixed, etc. Quite interesting (search on "OS X" on the main page to browse some OS X related issues, for example).
-rob.