If anything, a tiling window manager is exactly that sort of software: it has to please a wide variety of extremely picky power users and has to deal with tons

If anything, a tiling window manager is exactly that sort of software: it has to please a wide variety of extremely picky power users and has to deal with tons of corner cases--weird programs (the GIMP), weird layouts, multiple monitors, panels...etc. On top of that, it has to work well with an absurd amount of customization. The fact that XMonad manages all this with so little code is particularly impressive.