For me, focus-follows-mouse is most useful for terminal windows. It is a feature you can enable in iTerm2. This doesn't help across applications of course, and

For me, focus-follows-mouse is most useful for terminal windows. It is a feature you can enable in iTerm2. This doesn't help across applications of course, and there's a reasonable argument that the inconsistency is worse than the absence -- but for me, iTerm2's FFM feature helps.