Ubuntu 9.04 is booting faster, but are these optimizations being carried forward to the desktop and into general computing tasks? We used the Phoronix Test Suite to run a couple of benchmarks on Ubuntu 8.10 and 9.04 in the same configuration. The tests we ran were LAME MP3 encoding, Ogg encoding, timed ImageMagick compilation, IOzone, SQLite, and GnuPG.
In neither audio encoding test (MP3 and Ogg) was there much of a change in the encoding time between the two Ubuntu Linux releases.
Ubuntu 9.04 is just shipping with GCC 4.3.3, which is a minor update compared to GCC 4.3.2 found in the Intrepid Ibex, but because of improvements there or elsewhere in the updated Linux stack, the compilation performance was faster. With the Jaunty Jackalope it took nearly 20% less time to compile ImageMagick.