I use a wide variety of desktop and window managers, though I have never used XMonad, nor have I, to my knowledge, used any tools or applications written in Haskell, though I have at least heard of it.
I've been using UNIX systems since before the X Window System was even available (1982), and I used some of the very early Xlib implementations of X, the Motif implementation when it first came out, and fvwm when I first started using Linux based systems. Therefore, window and desktop managers that have some common traits with these environments tend to be the ones that I am the most familiar with.
I use KDE and XFCE about 50/50, and the two of them probably comprise nearly 90% of my desktop use. The remaining 10% I split between a variety of desktop and window managers. When I use a window manager, I probably use IceWM the most, followed by fvwm-crystal.
I use most of the major desktop and window managers at least a little bit, if for no other reason than to try them out. GNOME is way better than it used to be; years ago I did not care much for it; these days I use other environments mostly because of time spent and familiarity with them.