look at ground glass
You're right, this is an alternative, I nearly forgot about it. I use it to shoot macros of frog eyes as the dof is so tiny the af will never work. Imho it really depends on the vf size, for example I find it easier with my 6d than 60d. And for anything with less magnification, arguably af works better the larger the distance gets.
Another drawback of the fixed focus approach that you have to move the camera back and forth, this can be a problem if you're lying in the ground or standing waist-high in water and would rather keep a stable position :-).