Peter,
its 3d in some cinemas for some sessions
they provide the 3d glasses (new polarised system, not the old red and green colored glasses)
I felt the 3d effects were nice and mild in fact so that they just added a bit of depth to the movie subtly.
As H suggested you may be able to get a seat in sme comfortable setting but if you cant just pick a session first thing in the morning where there wont be anyone around in the theater, get an aisle seat and feel free to wander around every 2 minutes!
its a good movie.
The alien topless parade on tractors is amazing in 3d

frank