According to post #15 of this Ubuntu Forums thread about Nautilus being slow, turning off global menu speeds Nautilus up significantly. This is certainly true for me, as running Nautilus as root makes it a few times (!) faster (with no gnome-scripts installed, cache cleared, Dropbox turned off).
Now, I like the global menu--but I also want Nautilus to be fast! Is there a way to turn off the global menu only for Nautilus?