I only use the model M keyboards. They were the most reasonable approximation to the selectric typewriter that I own. IBM knew how to make a good keyboard.
Another thing I liked about the model M was that it had very low radiated EMI -- they thought about what they were doing. Test a cheapo plastic keyboard vs. a real IBM model M. If you are using a radio or sensitive equipment it's a big deal..
I found by accident years ago that my WPM goes UP if I use earplugs or headphones. For some reason, if there is no sound, I can fly. I would like some feedback on this. I had a product design psychologist comment on this and he thought there was something to it.