Because there is no right ctrl on a mac keyboard, some of these shortcuts are inconvenient. For instance, ctrl-A. Do you use your pinky or your thumb?
My Air has a JIS keyboard, so the control key is where your caps lock is. Most of my keyboards are configured this way (either physically or in software); on those that aren't, I use my opposing palm to press ctrl. I can't imagine using a Mac with flat keys and no right control =(
Because I make lots of use of control, I usually map Right Command to Right Control, so I can easily thumb control, command or option at practically any time.