I was about to make the same recommendation! I tried delta and difftastic and both were too much for me, so I've been using diffr as my git diff program for the past few years. It's delightful, thanks for making it.
Very nice, I've been looking for something like this since completing a port of DiffMatchPatch. I'll going to give it a spin right away, thanks for sharing your hard work!
As a bit of feedback, you might wish to put a section showing how to make a git alias for diffr, to complement the section on how to install it as the default. I know how to do this already, because I use delta and dft depending on what I need to see, but it would be useful to others to have a copy-paste solution handy.