Note also that 16:9 from iTunes means lower resolution than 4:3 since the horizontal resolution is fixed at 640 pixels. so for 4:3 you get 640x480 and for 16:9 you'd get 640x360.... Effectively 33% less resolution in the 4:3 section of the frame.
You know, someone said earlier that paying for a movie off the iTMS that you can't hold may not be entirely worth it. Now, I very badly want season 5 of 24, but I just can't bring myself to do it if they can't even give you the show in the full aspect ratio. It's a shame especially since the quality is just so much better now.