Note that ergoemacs is not the same thing as CUA mode. Ergoemacs is more about ergonomic efficiency than about mimicking windows. CUA mode is a separate mode already built into emacs.

I used ergoemacs keybindings for a year or so. They are pretty slick, and definitely more ergonomically efficient than emacs default keybindings. However, many modes are designed around emacs default keybindings, and I eventually decided it was too much work tweaking every mode I used to conform to the ergoemacs setup.

If you stick to emacs core modes which are already customized, it's probably a good choice.