I dunno, I'm guessing that NES hardware isn't that complex, so how much quality do we really need?
Upload your ROMS, insert the cartridge and start playing. Also has a save feature and includes Game Genie support. Pretty good to me.
Price isn't cheap though and not all games are compatible but it's way better than paying the ridiculous prices we see on Ebay and elsewhere. Way better imo. Not sure if it runs identical but from what I hear it does.