The limit of Nestopia X, as X goes to infinity, equals perfection
Also, blargg's NTSC emulation is the only way to fly. I am really picky about accuracy and the feel of actual real NES hardware, but blargg's NTSC emulation code has actual made me question the importance of keeping my original hardware. My closet full of hundreds of NES carts, several toasters, etc...
If you have a very fast computer, give NTSC emulation a try. It makes Nestopia look almost identical to the real thing!