Speed would be nice- most of the games that are worth emulating you have working. There's still a few graphical errors here and there in some games, and I find Majora's Mask is a little slower on my system with the OGL plugin than one or two of the other plugins out there (not to mention I still can't figure out why the 0.8.5 version of the plugin crashes on my system, but 0.8.4 still works fine. I reinstalled my video drivers and what not. Perhaps it's a Direct X 9 conflict or even an issue specifically with Windows 2000...)
So yeah, work on game speed and perhaps a bit of compatability on major n64 titles like Conker, Star Fox, PD, 007, and Majora. You've got a good thing going here and I hope you continue to work on it.
By the way, any chance for zip support on the next release of the emu? That's the one really nice feature besides a cheat engine I find TR 64 lacks. Cheat engine doesn't matter, but zip support would rock.