I've seen a load of 3D films and to be honest, the 3D doesn't add much and the dark picture detracts more. Its a gimick, as is Imax.
OK - I realise Imax is better quality but by the time you factor in how far back you have to sit, there is no benefit. You've paid all that money for nothing.
Your right. The only noticeble differnece for me with Imax, and it may just be the theater itself, is the sound is so much louder and more crisp. I find this funny in that you go to Imax for the view, but the sound is what is actually better.
Yeah, when I saw TDK in a regular theater the sound wasn't loud enough so the whole gag with the guns and Alfred saying "I don't think you made it loud enough" didn't even work. But when I saw it again in IMAX that part was really loud as clearly intended.
As far as the picture is concerned? There's definitely a benefit. I don't think it really matters how far back you sit, but in any event you can sit up front if you really want to. Take the opening shot of TDK as an example. This looked unremarkable on a regular screen, and actually looks slightly crappy on DVD. But on the IMAX screen it was a whole different ballgame. The greater visual depth provided by the format actually created a momentary sense of vertigo.