I find them incredibly ergonomic, another bonus is that it provides the same defaults found in most terminal emulators. Most people try to use pinky for Ctrl, or map to Capslock, but using the side of your palm for Ctrl is really comfortable. I generally run circles around colleagues in a terminal or working with text, especially when utilizing macros, but the learning curve is definitely steeper and took some time to get used to.

Universally.

Outside of Emacs, I have those "insanely bad" bindings in GUI text widgets, my shell prompt, when choosing/searching in in fzf, navigating scrollback in tmux, and inside REPLs of all flavors. Basically anywhere text is entered, I edit with those bindings. My Kinesis keyboard has 12 thumb buttons, and for me Control, Meta, Super and Hyper are all easily within reach.