Eh. I've used focus-follows-mouse and tend instead to strongly prefer the OS X method of allowing scroll events to percolate to the window under the cursor but retaining keyboard focus on the window it's currently in. This allows me to scroll, say, a web browser on my right-hand monitor, while continuing to type in the left.

Also, don't forget that OS X lets you scroll whatever window your mouse is over, even if it is "blurred" (not in focus). This is the one feature that I miss most whenever I need to use Windows.

The only people here who really seem to like it are the ones using drawing-tablets as their main input.