I've been wondering about this.
Last stable release was at April 28, 2006, 11 months ago. Of course I'm not complaining, but I do wonder when the next stable release will be, beta if you will. Seems like a lot has been done to the engine, but where does that end?
Is there any specific list of features that are still to be implemented, ironing out or are the developers simply adding things into the engine as it seems fit? I'd love to participate, implementing some feature that is still missing. Pretty sure there are many would-be contributors here, if not developers.
Would be interesting to review other engines and simply make a list of what would be good to have in jME, put it up and see if people are interested in implementing it. (that's how community work is done, right?)
Using a bleeding-edge versions of the library can be discouraging, but the cvs version is well managed though and is surprisingly stable. But if jME is to be used as a "default" game engine for Java, then it needs to gear up (IMO).
And let's not forget about tool-support, I feel like that is a crucial element that is missing. I envy engines that have a nice set of tools, especially the Torque engine.
Be nice 
Discussions are currently underway for the next release and what that release will be labeled. Expect something soon.
maybe you could give it a codename (like "orangutan"). i'm not sure if it might help users identify versions better, but it surely would be cool 
And I'd be much flattered