Ignore the Code: iPad Springboard Breaks Spatiality
On Ignore the Code, Lukas Mathis has written about what happens when rotating the iPad home screen. Read that first and look at the illustrations. (I think it’s always worthwhile reading Ignore the Code if you have any interest in user interface design.)
Out of the three ways of dealing with rotation, I think restricting landscape to only four columns is the best. Apple’s way is in the middle. Rotating just the icons does not seem right to me. To me, the content does not sit on the screen. The screen acts as a window. Rotating the iPad (or iPhone) should not rotate the content, just change the shape of your window and rearrange the content to fit better. I have not read the iPad or iPhone Human Interface Guidelines, which may have something to say on this ‘window’ matter.