Just wanted to share that I just integrated NiftyGUI into JME2 and it’s working really well.
When running all/intro.xml there are some glitches with a few images and texts are out of place or scale, but simpler tests are working nice. It is working properly both behind and in front of other gamestates.
Loos promising.
Thank you void256 for such a great piece of software.
uhm, thanks 
how did you do it? with the jme2 renderer that’s already available or did you create your own integration/connection to jme2?
With the RenderDevice, InputDevice and SoundDevice in the package de.lessvoid.nifty.jme that live in Nifty repository, against 1.2 stable jars.
Is that ok? Should I have done otherwise?
This will be the basis of several out-of.the-box JGF systems (console, settings screens, niftyview…) and will make JGF easier to plug to JME3 and PulpCore (if it ever makes it so far).
perfectly fine, no worries! 
congratz!