[torme]

I'm not an expert on this but I'm guessing with tomcat being so ubiquitous they do an initial release of the new version, and then it takes a few revisions out in the wild for them to deem something production stable. I think its the equivalent of doing release candidates ala Firefox but without the RC label.

[yycom]

This is really a much better way to do it than the arbitrary silliness of alpha, beta, rc, dev, etc junk. See e.g. ridiculousness of python's PEP 386. Nice and deterministic.