Widgets occupying the whole screen
According to the android developers guide


  This grid can vary by device; for example, many handsets offer a 4x4 grid, and tablets can offer a larger, 8x7 grid


That being said, most phones have a 4x4 grid. One exception that I know of is the Galaxy Note which has a 5x5 grid. Also I've read about custom ROMS or mods that change a default 4x4 grid to 4x5 or 5x5