SPOILER WARNING: Only the first 14 seconds of this video depict the use of the iPod, the rest is gameplay. Avoid if you have no desire to watch that portion of the video.
A random gamer who has scored an early copy of Metal Gear Solid 4: Guns of the Patriots has uploaded a video to YouTube that displays the functionality of the in-game iPod. While it would be cool to be able to utilize music from your PlayStation 3's HDD, there has been no confirmation on if you can or not.
We've included the video below and as indicated by the spoiler alert above, only the first 14 seconds include the iPod.