Mapping of arrows and some other Home-Ends to the right hand.
Once you tried to use ijkl instead of cursor keys (notice - these keys compose the same pyramid as you used to) - it is impossible to go back. It is invaluable when you don't have to take your right hand off the keys to navigate a cursor - you just use Right Alt (or Right ⌘) with ijkl and move a cursor without leaving right hand typing position.
Mac has many strange decisions but its ⌘+c, ⌘+v - is far far far more convenient than win/linux Ctrl+c, Ctrl+v because you can use your thumb to press ⌘ instead of pinky Ctrl. Once you used to it, there is no turning back.
TODO picture