What's new/fixed (most notable changes):
* Integrated MAME core 0.71
* Switched to a more aggressive handling of silent XBE dependencies. This change frees up almost another megabyte of RAM, which will hopefully get a couple more games working. This will undoubtedly break games that used to work until they are reported and thrown into the new families, but it gives up about a meg of RAM. To anyone who just read through that paragraph, please pardon the yelling:
THERE IS A VERY GOOD CHANCE THAT THIS BUILD WILL BREAK SOME ROMS THAT WORKED BEFORE! THIS IS A CONSEQUENCE OF AN AGGRESSIVE STRATEGY TO RECLAIM A LITTLE MORE RAM. PLEASE, PLEASE, PLEASE REPORT ANY ROMS THAT HANG/CRASH!!
Just had to make sure that everybody gets at least that part, if you guys don't report the bugs, I don't find them and can't fix them for you :) * Added a START menu to the Launcher. Many actions that were previously accomplished via shortcuts are now performed by pressing "START" and selecting an item in the menu.
* Integrated new graphics from r4dius and cleaned up the layout of the help/options screen.
* Fixed a problem where BIOS games were hidden when "clones" were filtered out
* Added several ROM filter/sorting options, these may be changed via the Options menu. Filtering is toggled with the BLACK button.
* Put in support for rom colorization/filtering on ROMSTATUS.XML (This file will become available to the general public when the new site goes live). See the addendum below for info on the format of this file for the adventurous testers out there :)
* Fixed the problem where moving a ROM to the backup directory would not remove it from the ROM list cache file.
* Changed the functions in the MAME core that ask for memory to use a wrapper function where we can properly catch out of memory conditions. This makes the system far more stable, and as a bonus, we can print out a sensible error message (Out of memory) instead of asking you guys to learn the 20 different messages that really just mean "Out of Memory"
* Added VSYNC option
* Added frame throttling option
* Increased autoframeskip reliability
* Removed history.dat support (we might add support in the Launcher in the future, but in-game history is probably out of the question, sorry for getting everybody's hopes up w/ the last release).

Full change log here.

Official Site: http://sourceforge.net/projects/mameox/
Download Sources: here
Download Binaries: n/a (built with XDK)