> Coordinating both hands to press key combos seems much harder than doing that with just one hand.
Anything is harder until you get used to it :-)
I had to make the shift. It wasn't really an option for me. Life improved after I made that shift.
> Also, in many cases (unrelated to Emacs), one hand is on mouse
While this is unfortunately true, it is still considered unergonomic by most ergonomists (any mouse use is unergonomic if it is continuous). They always recommend using the keyboard if the mouse can be avoided.
In a past life I did CAD work with a mouse. Horrible ergonomic issues ensued. Life got a lot better once I switched to programming.