Dear Dave,
I usually just follow the release versions (although I largely use
Tomcat and not JBoss). For Tomcat at least the number of releases is frequent enough so that patches to problems I see are available in a few months as part of a release version.
I am very reluctant to patch against an SVN version and take that in production. If Tomcat releases slow down to the point where I need to start doing so regularly, I will switch to an app server that brings out releases more often. I expect app server vendors and communities to provide me with a functional whole server, and most do.
I know some big names like to bring out app servers as a base release and then a long list of individual file patches. I really don't like that model, because it means that you a) don't have the same version as everyone else and b) don't know if you did it precisely right and in the right order and nothing silently failed and c) you don't really know what actual version you have.
Kees Jan