I was skeptical at first but now really like it.
* Can quickly ("analog-y") adjust brightness and volume. Similar to a volume dial in a car vs. up/down volume buttons. In 2 seconds you can dial it in.
* YouTube videos (in Safari) have the playback controls in the touchbar, not in the interface. You can watch a fullscreen video and scrub through / jump around while keeping your real estate
* TouchID is really nice with 1Password
* I can see things like Pomodoro timers, etc. being useful in the touchbar. I haven't looked at extensions yet.
* Things like the print dialog have a big, colorful button. It immediately stands out and highlights the most common action from where you are in the program. "I don't need to hunt around to adjust margins, paper handing, I just want to print."
* The escape key has a larger hit target than is shown so you can still use vim effectively.
Overall, for developer tools, I'm willing to invest in even marginal gains if it makes my life better. We use these machines hours every day, for years.