Guess this is as good a place to mention one plan I have.
What I'd like to do is possibly produce a version of WolfMAME with many extra features, which would be fixed at a set MAME version, so that work can be focused on that, without having to worry whenever Aaron decides to re-write something.

It'd probably all start as just a MAME frontend, probably GTK+ based (for easier compatibility with other OSes), and eventually tie it all together, perhaps even having it all integrated together (a la MAMEUI). I'd probably use no later than 0.116, due to INP playback issues with the re-written Neo Geo driver. None of this would affect the usual WolfMAME release for each major MAME release, either.
This is all still in the fairly distant future, though, I'm still working on MESS for now, and I'd like to get back to my other emulation project that I've neglected for the past 18 months, too.