The Java 2D Microbenchmark is one of our PTS test profiles that come courtesy of Sun Microsystems. Starting with the Java 2D text rendering performance, Mac OS X 10.6.0 was a modest improvement over the 10.5.8 release.
Like some of our other graphics tests though, the vector graphics rendering performance for the Java 2D pipeline had actually regressed under Snow Leopard. Again, hopefully this is something that will be worked out in the very near term.
Looking at the MP3 encoding performance with LAME, Snow Leopard brought a minor performance boost. LAME was running a few seconds faster, which will become beneficial and appreciated if you do a lot of audio encoding work.