Looks interesting, but also frustrating. Or is it just frustrating to the sloppy programmer? There are programmers who like to keep things tidy. There are programmers who have an extreme notion of tideness, and the latter group tends to like automated checks (think rubocop), in which the gem overcommit helps. Your commits will probably take longer before they actually finish, but the result is a very. clean. commit.
In general, overcommit supports quite a list of tools that I think are not required to run at every commit, but still are interesting to check out.