Ubuntu 8.10 took slightly less time at performing 12,500 database insertions via SQLite, but the difference was almost unnoticeable.
The 2GB file encryption performance using GnuPG was virtually tied between Ubuntu 8.10 and Ubuntu 9.04.
Ubuntu 9.04 is not being officially released until April, but already it appears to be in good standing. On the Intel Atom netbook we used for this round of testing, the boot time was shaved by eight seconds, which is quite noticeable. When to the desktop, in some areas like compilation and disk-intensive tasks there was also stronger performance. As has already been mentioned, if manually switching to the EXT4 file-system the results should be even more promising. However, these tests do not cover the 3D side of Ubuntu. To see how Ubuntu 9.04 is doing on the graphical front with Intel's driver stack, look at Intel Graphics Regressions In Ubuntu 9.04?
There are many other features for Ubuntu 9.04 such as its home encryption capabilities with Ubiquity integration, ARM-based netbook support, an updated X.Org stack, and an improved migration assistant.