Here's a precis list of things that TUAW and its users said in comments, and a few of my own:
1. Closing an application window, thinking it has quit.
2. Downloading an app and running it from the disk image.
3. Creating endless untitled folders
4. Using Safari's Google search to get to a website
5. Confusing the concept of wallpaper with screensaver
6. Double-clicking a window thinking it will maximise it, but instead sending it to the dock
7. Not understanding the usefulness of column view and leaving everything in icon view
8. Not using any keyboard shortcuts
9. Thinking that now they've got rid of Windows they won't have problems of _any_ sort on their Mac
10. Renaming desktop icons to random characters because they don't understand the difference between the enter and the return key on Mac. (Enter puts an icon into rename mode).
11. People trying to find the menus on a window, not realising they're always at the top of the screen
12. Trying to resize windows from the edge rather than the drag area on the corner
13. Trying to use the CTRL key rather than CMD key for shortcuts.
14. Thinking it'll be easy to get a stuck CD out.
15. Installing a program every time they want to run it because they think the installer _is_ the program.
16. Where's "the internet"? (looking for the Windows Internet Explorer "e" icon)
17. Repeatedly hitting the Apple key expecting the Apple menu to pop up (confused with Windows Key and Start Menu concept)
18. Thinking the green "+" button maximises a window to full screen (not realising that Apple's maximise philosophy is to only make a window as big as it needs to be to comfortably fit the width of content currently being displayed)
19. Looking in vain for an uninstaller app, because they don't realise that uninstalling an application on Mac is as easy as dragging the program icon into the trash.
20. Minimising windows all the time rather than using "hide", leaving the document section of the doc littered with forgotten minimised windows (that are quietly occupying system resources).
21. Double-clicking dock icons.
22. Inadvertant click-drags and removing programs from the dock in the process.
23. Saving everything to the desktop or somewhere on the hard drive other than their home folder
24. Trying to load documents or programs multiple times because they don't recognise the progress indicators (sound of hard drive grinding, CD spinning, Mac spinning beachball, browser status bar)
25. Not understanding that the dock is used to both launch and return to a program …
26. Inability to work with multiple documents on-screen at the same time, because they have only ever learned to use Windows' maximise mode which always makes everything full-screen
27. Confusing "delete" with "backspace" (because Apple has two keys named "delete" on the keyboard, one of which does forward delete and the other backward delete. Way to go, usability geniuses).
28. Expecting "home" and "end" keys to go the beginning and end of a line, rather than beginning and end of a document.
29. Not realising that when you copy a folder over an existing one, OS X -replaces- the destination folder rather than merging the contents, which is what Windows does.
30. Looking for the "complicated" way of doing everything. For example, trying to go into system preferences and right-clicking on the networking icon in order to find available wireless networks, rather than just clicking on the Airport icon in the menu bar and selecting the relevant wireless network.
