I don't know exactly what the new features are, but a new version was released a few days ago.

http://mess.emuverse.com/

If you haven't tried MESS yet, well, I don't know what to tell you. It's really good in that it works much like MAME but for console systems. All of the controls and features, the same. The problem is that it takes a bit of work to get set up. You need to tinker with it. You need BIOS files. Screen shots aren't possible for every game, even if you have them... it takes some getting used to. Still, for some systems, particularly the Atari 7800, it's a great emulator - and for others, it suffices. If you LOVE MAME, you should at least give MESS a look.