My experience with trying to focus using the microprism/split prism on my Canon F-1 without my glasses on is: I can't. Maybe with the split prism, if I have a very contrasty vertical line to work with, but I can't even *see* the "out of focus" effect on the microprism part with my eye unaided, and determining peak focus on the ground glass is pretty much impossible.

On the other hand, I do trust the focusing when I have my glasses on. If I miss focus it's usually because I was rushing it too much. For landscape type subjects I'll often just use hyperfocal distance for the next larger f/stop to the one I'm set at. I've tried zone focusing but have only had some success at very small apertures.