filters (except Blargg's NTSC one) suck because they make the result different from what I was able to see on the real thing.
if I want super-smooth edges and blurs, I'd play a PC first person shooter, not an old SNES game with any HQnx filter

that said, it would be great to try to create a generic NTSC filter which could be overlayed to MESS systems supposed to be connected to a TV