I've recently started to help out with GeSHi and concentrated on pushing the performance higher and higher. What does that mean?
version | average speed (5 runs)
------------------------------------------
1.0.7.20 | 5.72 kB/s
r1400 soon 1.0.8 | 49.27 kB/s
------------------------------------------
So the new GeSHi is nearly ten times as fast! And don't forget 1.0.8 also has bugfixes, more features etc. etc.
Oh and btw.: Peak memory consumption is down one megabyte as well!
I can only say: GeSHi is _the_ highlighter for the web. Even more so with support for more than 100 languages and decent performance.