A GNOME 2.12 preview

With the RENDER extension it should be better in that situation, since old gtk would have pulled down the pixels from the server to the client, composited, and pushed pixels back; compositing can now be done on the server instead, avoiding the round trip. (Performance of networked X11 is usually a function of number of round trip requests.) Cairo automatically uses RENDER or not as appropriate.

None of this drawing work does anything for some of the common stuff that shows up in gtk profiles though, like text measurement. The complexity of Unicode and international font rendering isn't at all easy to make fast. This stuff is a client-side issue not an X server or drawing issue though.

A simple example, most programmers have probably written a word wrap algorithm before - insert a newline at the last whitespace before the wrap column. Maybe a dozen-lines function or something for ASCII, and super fast. But 100% broken in many languages. Welcome to the real world. Ouch. The same thing happens with a lot of text-related operations.

Honestly though, most apps are not bottlenecking on drawing text (or GTK+ in general). In practice the speed of an IMAP server or web page loading/rendering or pulling executables off disk are all much more user-visible issues.

Some of the "snappy feel" people are looking for will be much easier to achieve with new X server features that cause it to retain window contents and avoid the flickery expose event model. This is qualitative change (avoid intermediate redraw states) rather than quantitative (do the redraw as fast as possible).