I got ahold of one these a few months back.. NTSC model, it works so far as I can tell, except that the graphics are scrambled. At first I thought it was an issue with the converter and a general lack of compatibility with NES carts but then I got ahold of some Famicom games and they're not displaying right either. Note that both Famicom carts are Konami games, but one is a pirate.
I've tried cleaning all contacts involved in the 'circuit' (the yellow adaptor, the GTA port, the carts themselves) and nothing's resolved. I dread opening the unit up for fear of getting the screen contaminated, if anyone can negate those fears I'd be much obliged.