I agree on some points - getting a bad screen or keyboard will make using the machine painful - get good ones. Investing into a faster CPU or GPU is a complete waste of money. Most of the cheap machines try to give you a fast CPU while skipping on the important parts.
I found chromebooks to use decent hardware where it matters and skipping on the rest.
Faster CPUs are always nice, however. I wouldn't consider them a waste of money for a development machine. Even web browsing is improved by a faster processor, however.
Having owned both, I can. Not so much with web browsing but with compile/test cycles, every little bit makes a noticable difference. (Remember when Linux kernel compiles took 20 minutes? Now 20 seconds feels like a long time.)
I found chromebooks to use decent hardware where it matters and skipping on the rest.