Come and grab the latest official "stable" build of MAME from the Latest Release page, or from the ZTNet Mirror. As of this release, I am officially producing a 64-bit native Windows binary along with the usual 32-bit builds to help encourage more testing of the 64-bit native code. For the most part, games run at least as well as the 32-bit versions, and some run significantly better thanks to the architectural improvements of native 64-bit mode.
Another notable change with this release is the movement of some core shared files in the source tree. A number of files in the mame/machine and mame/video directories were really more core shared components, and so they have been given a new home in the emu/machine and emu/video directories.
As always, report bugs with this version over at MAMETesters. Have fun!