As am I. I found some expensive hardware solutions that do eye tracking but can't justify the expense to see if they work. Other systems include mounting a dot in the middle of your forehead and moving your head around...impractical for most cases.
I've always found focus-follows-mouse to be a detriment rather than a boon. If I'm going to mouse over a window, it's trivial for me to just click the window, but using your mouse cursor to change window focus seems vastly less efficient than using the keyboard.
What time savings do you find that you can't key with keyboard shortcuts?
The awesome thing about focus-follows-mouse is that it doesn't raise the window that gets the focus (which clicking in it usually does). So I can type into a partially hidden window, while keeping another window on top.
For example because the window on top is a web browser and I'm referencing some API, or the window on top is another emacs window with another module I'm working on that I'm using, etc...
So I can tell the window manager where I want to type, decoupled from what windows I want to be stacked on top of each other in what order...
And, for example, right now, I have 6 emacs windows open for the project I'm working on, plus a few terminals to run the code, plus firefox. I don't see an efficient way to quickly shift focus to what I want, without tab-ing through all the windows looking for the one I need, potentially messing up the order I have the windows in...
Also, for me personally, using the mouse to tell the computer what I'm looking at, while the keyboard tells the computer what to do there is almost instinctive...
The result of more hours spent playing FPS games and the like than I care to think about. At one point, sitting down at a computer, without thinking about it, my left hand would automatically land on wasd and my right on the mouse XD
The behavior I like is more mouse-wheel-follows-mouse so you can move the mouse over to a web browser and scroll. Especially with a touch pad. Windows still treats the mouse wheel as part of the keyboard.
Cmd+backtick only works if you're switching between windows of the same application; if you are, it works well. However, I find more often the case is that you're not. (In my case, it's usually between the terminal, the browser, and the editor, or some subset thereof.)
Cmd+Tab switches only between different apps, and brings to the foreground all windows of that app, even if only one is required, sometimes obscuring way more of the now-backgrounded window than desired.
I really miss having a key to switch to the next window in the Z-stack, ala Alt+Tab on Windows/Linux.
Unfortunately kwm cannot do real focus-follows-mouse, it can only raise windows to the top. That works okay if you're using tiling mode exclusively, but with floating windows it's unusable.
Coming from i3, I tried Amethyst for a while when I had to use a Mac at my previous job. It seems like the best solution within the constraints of OS X, but it always seemed like enough of a hack that I ended up battling both it and the real window manager, so I ended up disabling it after a few months. The focus-follows-mouse never came close to working as expected for me.
Fighting with window size, positioning, and focus is such a productivity killer. Now I'm glad to be back in a real tiling window manager.