I'm a developer, and the only key I routinely use from the top row is escape, for vim. (And Ctrl-Alt-F1 to drop out of X11 on a Unix system... but that's not applicable here.)
Anyway, it looks like you can still put a virtual escape key on the touchpad when Terminal is active. Or if you want a physical key, you can also remap one of the other modifier keys to act as escape.
In IntelliJ, Visual Studio (through Parallels) and Chrome, the Function keys allow me to step through the debugger. It's pretty standard in my day to day workflow, and they all pretty much use the same keys.
Esc is pretty useful in vim and it's used frequently in Windows. I could remap a key, I just don't like being dependent on custom layouts since I sometimes have to switch between machines and I'd rather it be as consistent as possible.
* F5 - Refresh(Works in many applications.)
* F6 - Cycle through input box focus in Firefox.
* F9 - Expose, All Windows
* F10 - Expose, Current Application
* F11 - Expose, Desktop
* F12 - Dashboard
Plus many other function keys that are application dependent. I started with function keys in MS-DOS and Word Perfect since it came with a keyboard overlay.
I think the touch bar design is fine, but I doubt I would get enough value out it to make it useful enough to me while not making me regret losing physical function keys. They kept a 13" model with function keys, which is the size I prefer, so it will be fine into the future for me.
F5 - CMD+R is standard in MAC. I haven't used F5 in years, and I just tried it (didn't work).
F6 - Like TAB?
F9 - Well there is something like this on F3 but I never used it. I can do this with hot corners in mac, way easier.
F10 - Same like above
F11 - Same like above
F12 - Not sure, never used dashboard in osx.
This being said, I am sad for the removal because I use the top row a lot for volume/playback/brightness/esc.
F5 does not work in Chrome or Safari, but works in nearly everything else I use.
F6 - It is a tabbing functionality for application input boxes, but related Firefox and other applications with similar design.
I actually have the top left corner set to do Expose all windows as well.