As you can read in my earlier response above, I believe that Apple is using EXIF for jpg file orientation of still photos.
Apple is certainly using something for providing orientation information for still images and videos. I have recorded about half a terrabyte of video per year with Apple iPhone and iPad 2 cameras, and am looking forward to using the new iPad 2S ( or iPad 3, what ever it is called) and the new iPad 5.
I take my videos in landscape mode with the home button on the right, with the + and - buttons on the bottom left of the iPhone 4S or iPad 2.
Apple provides developers with a software known as QTKit which automatically provides orientation metadata to the jpg still photo files and mov video files.
I have no idea if QTKit is writing EXIF metadata, or some other orientation metadata, in the jpg and mov files, but it is certainly writing something that orientation aware software in the Windows and Mac development world are able to read.
I am mildly curious about what orientation metadata Apple actually appends to the camera files. If any reader of this thread cares to provide such details I will be greatly appreciative.
At the end of the day, I do not need to know, as I know how to hold the camera so that orientation is not a problem for those I send images to, and I know how to open and save upside down, or sideways, images other folks send me when they hold their iPhone camera in one of the other three out of four of the possible home button locations.