About 14 seconds were shaved off the GnuPG encryption time using Ubuntu 8.10 and 9.04 over 8.04.2 LTS.
Intel Atom hardware is designed for general computer usage and not any ray-tracing, but should you be interested in ray-tracing on your netbook, the newer Ubuntu releases improve there too. For measuring the ray-tracing performance with the Phoronix Test Suite we used C-Ray, which is a very simple ray-tracing engine. The C-Ray performance had regressed slightly in Ubuntu 8.10, but in Ubuntu 9.04 the performance is improved by more than 25%.
The RAMspeed performance is much better with Ubuntu 8.10 and Ubuntu 9.04.