The conversion looked great when I saw the Avengers trailer before John Carter in IMAX 3D. Made me want to run right out of the theater and get in line for Avengers. The shots of Iron Man flying through the city and the shot with the pan around all of the heroes looked really fantastic in 3D.
I'm a big fan of 3D and as long as the theater gives you an option, I hope I can continue to enjoy it for many years to come while those that don't like it can go to the screen next door.
Also, maybe they can make the 2D showing have mono audio instead of surround sound. I've heard of people covering one eye so they don't have to see the 3D picture--maybe they can also cover one ear so they aren't equally bothered by 3D sound.