It's easier to put a port on something and never use it than try to make an addon device in the future and have to do some strange hack through the controller ports.
Whats the point? You can put every NES rom out there on a PSP memory card and play them on that. Or maybe a GP2X.
The point is to play on real hardware. Anyone could emulate NES on any platform they want. If you just want to play games and don't care how, emulation is fine. But others would prefer to play on the real console, especially people that code their own NES demos or games. Remember this cartridge was made by a guy that is on the NESDEV.com forums. That's the intended audience. I just wish he'd made more cartridges. =( The "Lite" version can't handle MMC3 plus you need a CopyNES system so I see no point for me.
orderd mine as soon as they were avaible been waiting for it about a week now (+20yrs if you count the time I've waited for a product like this) :O