I don't use an ergonomic mouse. I am using my keyboard probably ~20x more than my mouse, so it just doesn't seem that important. Mostly I am using my mouse to scroll around and navigate webpages, but when coding it's mostly Vim, tabbing between windows, typing commands in the terminal, etc...

There are other ways to deal with that, like physical conditioning. Ergonomic keyboards don't cut it when you need to carry a laptop.