It would be useful to have the ability to undo something that may have been accidentally typed into a highlighted cell.
For example: I tabbed into a populated cell that had the number "10.81" and I bumped a button which made the cell say ".0" I don't remember what was there to change it back. This is not good when editing payment information. In Excel and many other programs, if I were to press the "Esc" button before exiting the cell, the cell is repopulated to what used to be there, kind of like an "undo" option. Or just the ability to "Ctrl+Z" something would be nice.