Thanks :)

The only multi-input game I have right now is Tetris for 2 players. My girlfriend doesn't complaint while playing it (except when I win :P), so I'd say it's pretty responsive, even with the somewhat convoluted way the CPU communicates with the PPU and the double-buffering.

I think it will work for other types of games as well. With all the hardware, firmware for the 3 microcontrollers, bootloader software, compiler toolchain and tools, I still haven't gotten around to actually make a lot of games for it.