I saw the U23D movie tonight. I loved it.
I am not a huge U2 fan, but I have always liked them. I remember hearing them for the first time in my freshman year in college in 1980. One thing I like about them is the clean sound with just the four band members.
The movie is a 3D version of a concert in a huge venue (looks like a soccer stadium in Buenos Aries, Argentina). The 3D effect is used very well. It makes you feel like you are there, but there are very few gratuitous 3D things reaching out to you from the screen.
The sound at the IMAX theater was fantastic. The bass was thumping through the theater seats the whole time. It was pretty loud, but certainly not as loud as a real concert.
My favorite songs from the film were New Year's Day, Sunday Bloody Sunday, Pride (In the Name of Love), and With or Without You. If you like U2, you should really see it. It's only playing in IMAX theaters and there are no plans for a DVD release.