ability to see cell calcualations in view mode
You currently can't see how the cells are calculated, unless you are in "edit workbook" mode. It would be nice to see how cells are calculated because I need to share a sheet with others so they can see the calculations, but I don't want them to edit the sheet.
In addition, there's no easy way to view data which doesn't fit into its cell while in read-only mode, e.g. a long text string. (You can copy and paste it elsewhere, but that's hardly user-friendly...)