Re: iTunes/iMovie using AAC protected Tunes
For what it's worth, I burned a DVD last night with a protected iTunes song (.m4p) in it, and I had no problem playing it back on my regular DVD player. This is with the latest version of iTunes and the iLife '05 suite on an eMac with a super drive.
One thing I noticed in working with protected songs in iMovie: if you create a new project in iMovie and add a protected song to the timeline, iMovie will not let you export (via the "share" menu) the song by itself. I suspect this is to prevent people from using iMovie to strip off the DRM features of iTunes. However, if you add a video clip of greater or equal length, iMovie will let you export the combined clip to any format you want.