What U23D did make me wonder is why all movies aren't in Imax 3D (some say that's not far off); having a 60-foot Bono reach out to you while staring into your eyes is a pretty cool experience (or a freaky one, depending on your perspective). The gimmick is a thrilling format for a concert film - especially one with the massive grandeur and theatricality of U2.
Swooping crane shots allow the audience both an intimate view of the band members playing and a chance to look from the stage's vantage point out over a stadium of thousands. And the songs - almost entirely big hits - sound great (the volume and clarity of the sound matches that of the screen).
If not quite the same as a real concert, U23D is an event - and a must for fans of the band.