I used to use SourceTree. I moved to using GitX: http://rowanj.github.io/gitx/ and seem to prefer it much more. SourceTree feels too cluttered. Gitx has better UX and appeals to me as someone that prefers to view more relevant content on the screen.
... and has a Mac, of course, which rules it out for many of us (though I can't speak for the sdfjkl).