I noticed that they have a list of plugins here: https://wiki.mozilla.org/Bugzilla:Addons#Integration_with_Source_Code_Management_programs
...But most of those seem either outdated or barely above a simple utility/script as opposed to actual "scm integration". Anyone here use SVN along with Bugzilla here?
What capabilities do you require that something like scmbug doesn't do? I'm not really certain what you expect integration to really mean.
I think generic integration solutions are less important now because of the hooking capabilities of both Subversion and Bugzilla. Using Bugzilla's web services, you could add a pre-commit hook that communicates with Bugzilla and decides whether to let the commit proceed. You could add a post-commit hook that updates something in Bugzilla to show the commit. You could add an extension to Bugzilla to do whatever in Subversion when a bug has been resolved, but that strikes me as being a dicey proposition.
I think that you want SCMBug and possibly also the "VCS" extension. (I believe both are listed on http://wiki.mozilla.org/Bugzilla:Addons.)