Woohoo! Serious progress on the glyph cache. You can check out my most recent code from nautilus/librsvg. The new test rig (test-ft-gtk) shows quite decent performance, and I'm not done optimizing. It also has a nice, pretty display when used with the xdvng.pfa font from itrans.
This test shows that client-side rendering of aa text is probably a lot more reasonable than many people think. Of course, when the Render extension happens, aa text will be almost indistinguishable in speed from xlib's current text.