McNeel’s process for developing new versions consist of several steps:
WIP (work-inProcess) - starts from previous version current release (mostly) and begins adding new stuff and making major changes in old stuff to make it better. New WIP released for tryout every week (usually). Pretty much works but users may run into things that are just plain nuts and dangerous to their models. Not recommended for production use. This stage usually lasts for years. But it’s fun for users to experiment with and McNeel benefits from the comments and suggestions they provide.
BETA: the last stages of development for a new version. No more new stuff, just cleaning up the new stuff that’s already been added, completing documentation, and all the other things that surround the release of a new product. Usually pretty useful but you are still on your own as to whether you want to use it on real projects. Still released weekly. Stage lasts many months - probably should last longer than it usually does but McNeel gets anxious and probably needs fresh money.
RC(release candidate): McNeel thinks the product is ready for release. Stage lasts a couple of months or so. Opportunity for users to get in their last licks.
Release: Now you need to spend money to buy it if you want to continue using the new version.
Post release: McNeel continues to release new RC’s on a more or less weekly basis with bug fixes, feature refinements and the occasional minor new features. The version number increments to the right of the decimal point as minor revisions. When they think the RC is to an appropriate state of readiness and reliability they will call it a new minor release.
The only versions that McNeel believes are truly production ready are the actual releases, ie: 6.00, 6.01, 6.02, etc. They are getting close to releasing 6.30.