The 1.2 series of Mumble is now entering the alpha stage. It has actually been pretty stable for a while, but now all of the major new features we want in 1.2.0 are in place; see http://mumble.sourceforge.net/1.2.0 for a summary. The only thing left now is polishing and bugfixing, and that means more testing. So if you want 1.2.0 to happen faster, simply download and try it. The client will show a summary of focus areas for testing when you start it.
The snapshots also include a 1.1.x compatibility client, and we consider this stable enough that we recommend people use is instead of the 1.1.8 client, as it solves a few problems on cutting edge operating systems.
The alpha clients can be downloaded from our homepage at http://mumble.sourceforge.net. Have fun with it, and we look forward to your feedback.