I currently have a DVR/Mame Box being made at the moment, I'm just waiting for an opportunity to get myself a good cheap HDTV for it.
For the UI, I personally used
MAMEWAH as it not only lets you launch games straight into Mame but it also supports emulators for other systems. The UI is skinable very customizable so you can make it look pretty nice. Could even make it into a DVR box if you wanted.
As far as using a wireless 360 controller. It's fine if you intend on not using the triggers and all your emulators will accept dpad input from hat POV inputs. If they don't, you're gonna need to find special drivers for it which was something I had to do to get trigger macros working for FFXI. I don't know where these drivers are offhand, mainly because they're Japanese. >.>; Someone else might know though.