I have been using Emulaxian for a year and am still in love with the thing. Doesn't get enough talk on this board as far as I am concerened, the thing is so chock full of options you can do whatever you want - even the choosing the game using the P1 fire button (and scrolling using the joystick).
http://3darcade.mameworld.net/It may seem overwhelming at first when you look at it, which I wonder is why more people don't use it, but right "out of the box" the thing works great without any invovled setup at all.
One last declaration of love to this front end (how bad does that sound!

), the person who writes the front end (Peter) is awesome. Ive sent him questions via email, at all hours of the night/day, and he always seems to answer within minutes. I am telling you, I've sent him an email at 3am (his time) and 3:20am I have an answer. Also, I sent him a "how about you add this to a future release" idea, and within a week he sent me the beta version of my idea to test out.