The slow rates are no longer a problem on fast machines.
(Mine goes full speed),
and some stuff which I have noticed with it (other say they haven't seen this), is that textures aren't correctly aligned into each other (you can see some black parts and stuff in them), this especially in mario64. Also, the background and the hand in mario is missing for me.
Last time i checked, some games refuse to run and just gives a black screen. For me, i tested mortal kombat triolgy (it was a bad rom, so i'm not sure here), and bettle racing.
Mario kart was missing almost all textures.