TortoiseHg - mercurial in TortoiseSVN GUI
Actually CLI is awesome for developement - I like it better than any IDE. However I like netbeans and eclipse when it comes to Java developement.
Of course nothing happens, they’re comments, but after few generations of those they just make things harder to read
About bazaar - I don’t consider it as mature. On other hand, mercurial is used at Mozilla (moved from CVS), by python developers (moved from SVN), OpenJDK, Atlassian (large project management software developer, moved from SVN), Google and many, many more. Git is used by Linux Kernel developers, Android, Ruby on Rails, KDE, Gnome, Debian, and many, many more too. I personally prefer mercurial with it’s ease to use for beginners and being powerful for advanced users, not to mention fantastic extension system (look at Mercurial Queues and HgSubversion), however both git and mercurial are fast, powerful and used in large scale projects.