This is easily the most visually stunning film I've ever seen. Even if you take away the 3D and IMAX enhancements (which were awesome), the level of CGI and cinematography were above anything I've ever seen.
James Cameron still has his wonderful knack for great storytelling, and although the plot can get a little preachy (love the environment stuff), there is never a dull moment and you are kept wondering how it will all turn out.
This has to be the leading contender for best picture of the year, and if it doesn't win, I have got to see what does win. Great film all around.