I recently saw a thread about Apply locking the ability to play HD Videos on iPod touch and iPhone, which does seem to be the case. I went to watch NIN in Manchester on Tuesday and took some HD Video, which was recorded in .MP4 format. I tried to drag and drop the video into iTunes, but it says something like it doesn't support the video, and even SSHing into the iPhone puts the video on the device, but you can't play it. If you install dTunes and drop your HD video file into /private/var/mobile/library/downloads, it works no problem and looks very nice on the smaller screen with such a high resolution! I'm clueless to why Apple wouldn't simply support this in the built in media player... but there you go!