I'm not sure if I'm calling it by its correct name, but in the old pre-Mavericks Numbers, when you were writing in a cell, if it's the same thing as an earlier cell, the cursor would automatically suggest what you'd written in another cell. You can continue writing what you want, or choose to use what was suggested. In the new Numbers, it doesn't do that. Is there a way to turn it back on? I actually use it a lot and it's especially useful to make sure you're not repeating yourself or making duplicate cells on large spreadsheets.