While EXT4 causes some test results to be clobbered compared to EXT3 or EXT4 on earlier kernels, in some tests it continues to shine. With the 4GB writes in IOzone there is a 34% improvement in the file-system performance between 6.06.1 and 8.04.4 and an additional 25% boost when running the EXT4-backed Lucid Lynx.
The 4GB read performance between Hardy's EXT3 and Lucid's EXT4 is nearly the same, but between the Dapper Drake and Hardy Heron revisions there is a 47% jump in the disk read speed.
There was not much of an improvement between 6.06.1 LTS and 8.04.4 LTS (only 6%), but there is nearly 50% increase in the disk speed with Ubuntu's 2010 Long-Term Support release.
FS-Mark was negatively impacted by the move to EXT4 and any other kernel changes between Ubuntu 8.04 and 10.04. Ubuntu 8.04 carried a small boost in performance, but that was more than wiped away with this newest Ubuntu Linux release.