a cursory glance at the screenshots there show it similar to git gui / gitx or similar.
I'm talking about fundamental interaction with the version control system, not a pretty gui. git has pretty gui too.
It's not just the GUI - bzr has one of the better-designed command line UIs too. It's very similar to Mercurial's, plus some nice things borrowed from other systems but integrated very consistently. (But I do agree that there's more to a VCS than UI design, and after the initial learning curve there's not a huge difference in command-line usage between the popular systems.)
I disagree. I found bzr to be a mishmash of poorly thought out options and features. A quick example: Compare bzr log's "-r" option to "git rev-list". bzr's "A..B" is stupidly inclusive on both ends making scripting very difficult.
If you want a really nice, consistent UI, check out darcs.