I've been wanting to try it for a while, but I'm just happy enough with i3 that it's hard to put in the time switching to something else. One thing I tried at one point and really liked in, IIRC, xMonad, was the idea of a "focused" window and then an LRU stack of windows behind that. I really liked that idea for the little bit that I tried it, but I found the configuration otherwise to be impossible to use (for me).