I made a switch from PC to Apple 4 years ago. The lack of meaningful keyboard shortcuts drives me mad. Consider a simple task of switching applications with the Cmd-Tab key: Minimize the only window of your application. Switch to another program, then cmd-tab back to your original program. Where did the window go? Oh, it's still sitting in the dock. So, grab the mouse, go get your window - and if you have 3 monitors (like I do), your mouse can be in a different zip code and it takes a long time just to find the cursor.
In fact, I think if we did this study today, we would find that due to bigger screen sizes, it's harder to spot the cursor, which would probably increase "mousing" time. However, Apple has 6 modifier keys on a laptop: Shift, Fn, Control, alt, option, and cmd, so trying to remember these keys can be a challenge too (and drives me crazy as well). What is the full screenshot shortcut? Control-Cmd-Shift-3 (aka finger-gymnastics)