Even as an emacs user, the answer is generally "No, I don't really use the function keys".

I mean, you're right that I use them to change brightness or change volume. But the touch bar can still do that, so... Meh.

It would probably be awkward to use for about a week, and then I'd get used to it. So it's kind of a whatever.

I do agree it's a dumb gimmick though, and is unlikely to offer anything more than the meme of running Doom on the touchbar.