You already had to hit the Fn key to make the Fn keys function, correct? The defaults were the brightness, volume, etc settings. You do the same thing and they all appear on the Touchbar. Zero change in usability there.
Generally I think most devs who use MacBooks disable that option (making it so that you have to press fn to get the standard mac functionality) so that they have better access to the Fn keys. I will echo the sentiment, that there's something nicely tactile about key presses that's missing from the touch bar. That being said - I do half my work on monitors using an external keyboard/touchpad anyway, so it's really not the worst thing in the world.