Eclipse usability is, and has always been, a very hot topic.
A working group has recently been formed to focus on usability across eclipse.org projects. There also is a very interesting thread on the eclipse.foundation newsgroup regarding the issue.
Yesterday, Julian Jones posted a historical review of usability in Eclipse containing a link to his EclipseCon 2005 presentation on Eclipse UI Best Practices. It's an informative read. Check it out.