Worst of all is system-cleaner -- or Cruft Remover, as its name appears on the System -> Administrator menu. The only instructions with this tool is that it "helps you to get ride of cruft," which might lead you to suspect that it is a feature like apt-get autoremove that removes packages that are no longer needed, or perhaps apt-get autoclean, which removes unneeded package files. However, during Intrepid's development, several users found that it deleted other packages as well. Sensibly, Ubuntu removed the package from the default install in the final release, but it is still available in the repositories when it should probably be removed for further testing.
These comments should not be read as unduly negative so much as fine-tuned. In general, Intrepid Ibex is no less usable than previous Ubuntu releases. The problem is that it is not that much more usable, either, although Shuttleworth's musings might lead you to expect it would be. If anything, its new features show how difficult it can be to address usability with breaking something else -- in particular, security.
Perhaps expecting major usability improvements in Intrepid Ibex is unrealistic. After all, by the time Shuttleworth began raising the issue of usability, the plans for Ubuntu 8.10 were already finalized and the first alpha releases were coming out. Under these circumstances, perhaps there was only time in Intrepid for minor usability issues, such as the tweaking of the arrangement of items in the Presence Manager menu that Shuttleworth mentions on his blog. If that is so, then it is Ubuntu 9.04, codenamed Jaunty Jackalope that will be the first release to reflect Shuttleworth's priorities.
Meanwhile, Intrepid Ibex is a worthy successor to earlier Ubuntu releases. But, like most recent Ubuntu releases, it's an incremental improvement at best, not a revolutionary one. And, if, like me, you hoped that the talk about usability meant that one distribution was finally getting the right idea, then it's a little disappointing.