The IMAX 3D experience was amazing, for 30 minutes or so I have to say any swift cuts led my brain to freeze briefly, but overall it was a totally fantastic piece of film making from a technical standpoint. I was actually extremely impressed that Cameron didn't JUST throw shots in for 3D wow-factor, his restraint was well used.
As for the film - well, I'd put it somewhere just north of predictable garbage. I wish Cameron (like George Lucas) would just let someone else write his scripts. He tells a good yarn, but some of the dialogue would shame a first year film student, and the last 45 minutes of the film is so laughable I thought it had descended into parody.