I'm bad and haven't looked at any of the JME3 code, but right now I'm looking for more of a high-level overview on what will be different in how JME3 works from JME2, and what might be involved transitioning from one to the other.
Still the same scene graph, game states, jme importer/exporter, etc? Anything absolutely amazing I shouldn't wait to try out? 
Keep up the great work!
cheers
JME3 does use never versions of OpenGL such as 2.0 or 3.0, instead of JME2 which use OpenGL 1.1. Also I believe it has better support for shaders since it's using these newer versions of OpenGL. Mokomo_Fan will know more though, since he's written it thus far.
We had a small team meeting very recently, and one of the things we discussed was the comparison between JME2 and JME3. There's been more talk and inquiries about it lately, so we feel it's time to crystallize the most significant differences, both feature-wise and architecturally. Stay tuned for an update
On a high level, jME3 is more modern engine.
It requires minimum OpenGL 2.0 support (Radeon 9500, GeForce 5 FX, Intel GMA 4500 and up).
jME3 is, in general, easier to use than previous versions, which means you need less code than jME1/2 to do the same thing.
There is a more detailed comparison being prepared as we speak so you might want to check it out when it's finished.
Cool, thanks for the replies!
I'm definitely looking forward to using JME3