Off the top of my head: - Resizing windows from any edge - Flipping the scrollbar direction - Automatically hiding scrollbars - Traffic light colored button

Off the top of my head: - Resizing windows from any edge - Flipping the scrollbar direction - Automatically hiding scrollbars - Traffic light colored buttons on windows - Whatever the three window buttons are now - The dock - "Close without saving" becoming "Delete" in some apps - Floating alerts versus slide-down anchored alerts These are all fairly minor, but there's a lot like this and it all adds up to things not quite working the way you expect over time.