DJ Legion installed MiSTer into a JAMMA arcade cabinet using an Ultimarc J-PAC and and gave a tour of the installation. He wrote a guide in the video description, complete with MiSTer.ini settings. This is probably the first of many MiSTer arcade cabs to come, and it turned out really well.
The J-PAC was a smart way to accomplish this, since it basically makes for a modular version of the add-on board that a lot of people have requested, which would theoretically combine a JAMMA control interface and Analog RGB output. Consider this a preview of what a future MR2JAMMA add-on board setup might look like.