We're getting pretty close to releasing Bugzilla 3.4rc1, now. There are only a few blockers left. Mostly they're just awaiting review. I'll also need some help with the release process for Bugzilla 3.4rc1, if anybody wants to help out.
The only significant changes since 3.3.4 will be a lot of bug fixes, a change to the Bug.search WebServices API, and the ability to hide the "See Also" field. The bug fixes are pretty important, though, so if you're using 3.3.4 you definitely want to update to the most recent BUGZILLA-3_4-BRANCH code regularly or update to 3.4rc1 when it comes out.
There are a lot of significant changes in 3.4 compared to Bugzilla 3.2, though. Those will all be listed in the release notes for 3.4rc1. The difference between 3.2 and 3.4 is not as great as the difference between 3.0 and 3.2 though. We're working on having smaller releases more often (starting with 3.4), and it seems to be working pretty well so far.
HEAD (Bugzilla 3.6)
On trunk (which will be Bugzilla 3.6), we've done a fair bit. There's a JSON-RPC interface, support for suexec environments in checksetup, and a lot of HCI improvements. We've decided that for Bugzilla 3.6, our focus isn't going to be adding major new features, but fixing up the features we already have. I wrote a message to the Bugzilla Developers List about it, a week ago or so, and I got a lot of positive responses (mostly on IRC or by private email). If you're interested in helping out, feel free to check out the list of bugs we'd like to fix for Bugzilla 3.6.