> The reasonable solution is to use one of the many native tiling applications for OSX.
As an i3 user (and former wmii user, and former xmonad user), I find it really frustrating to use tiling window management that doesn't support focus-follows-mouse. This rules out things like Spectacle, Divvy, etc. At a second level, I find that all of OS X's tiling applications have inferior support for workspaces on dual-monitor setups compared to i3/wmii[0] and xmonad.
Unfortunately, on Aqua (OS X), there's basically no way to do proper focus-follows-mouse support. There is one app that fakes it (I think Amethyst), but the latency is annoyingly high.
[0] heck, wmii has better support for workspaces on dual-monitor setups, which is saying something, because it literally doesn't have support for dual monitors at all - you can only run dual-head X11, which is a terrible hack.