Avatar blew donkey balls. And I even agree with Cameron's propaganda. The story just sucked, too simple and black&white. Yes, it was pretty to look at, but to me that still didn't save it.
I didn't used to think 3D was all that great, but it depends on the movie. It's more than worth it for some things. Immortals kicked massive ass in 3D.. and in RPX (or whatever) it was f#cking loud and amazing. My jaw literally dropped during that. Hugo was also an impressive 3D film, kid-friendly though it is.