My work machine has one, and I use it to display status information, give me a proper Rub Out key, and for soft keys to insert certain Unicode and macros that I need occasionally, but not often enough to remember.

I think it would have been better accepted if Apple make it more customizable right out of the box, instead of relying on half-baked solutions from tinkerers to program it.

In my opinion, it should also have been in addition to the function keys, not a replacement.