It is the only git client I know that makes polishing the commit history (i.e. moving commits around, splitting(!), rewording, editing) pleasant. If only it was available on Windows too...

True, it doesn't do everything, but it really hits the sweet spot for me. I wouldn't say that it almost has no functionality. To me, it has surprisingly much. It's just that it does such a good job of keeping the interface clean, that it can appear as if it doesn't do much.