Lightfight is fully playable. Entex Space Invader and Mattel Funtronics Jacks are responsive and do some stuff right, but are very buggy overall.
I think the MCU emulation core is not perfect yet. I did fix some small bugs there(eg. Space Invader didn't boot at all at first), but I don't know enough of COP400 (yet) though to see where the problems are. COP400 emulation core is here: http://git.redump.net/mame/tree/src/emu/cpu/cop400