Luckily, my old fix still works, check out the new version, here. Once you associate the M3U with the iTunes Opener program, it’ll intercept M3Us and load them into a new time-stamped playlist and play them in order and prevent adding them into the Library.

iTune’s default way of playing playlist songs of course is to insert them into the Library and not play them at all (after the first song it plays in your Library order, not the playlist you originally requested). It just works, right?