I use a Magic Trackpad, but I've used a mouse before and it was also acceptable. You figure out where things are pretty quickly.

But also I switched to Vim and TMux so that I would need to take my hands off of the keyboard less.

I just use the MacBook trackpad; works fine for me. And yes I touch type. If I couldn’t I would struggle. When I was in primary school (in the 80s), I had a choice from our municipal in the Netherlands between learning to touch type and something else (I forgot) or nothing as extra curricular. I am still happy I picked touch typing! Gift that keeps on giving.

Not sure about mouse operation, but the touch typing is mentioned in two separate sections:

1. Yes, you have no vision of the keyboard, so learning to touch type is essential

2. Lying down position, right hand on laptop keyboard, left hand on external USB keyboard (two-handed touch typing).

They've committed wholly and solely to pursuing this solution.

Not the parent poster, but I'd assume that most developers who are working with a laptop keyboard+touchpad can do it without looking down. A mouse would be more difficult, that's for sure.