I never had a NES, so I don't expect anything special. This looks great.
Although I did not try your program, I know that proper emulation of a complete system is difficult to achieve.
I did had a glance at the source code however. Well, it's lacking a more detailed documentation (though I think I'm not the one who should be doing this kind of comment
). Well, I suppose it's fine as long as you can find your way in it.
Good luck for the third release.