So I just say Avatar in IMAX 3D Friday, and man, was this great movie. 
 
This is truly a movie for all the geeks that grew up in the 80's who are now grown up and want more than just an "action" movie.  I will admit, the story is pretty by-the-numbers but the trick is the execution and this film is put together masterfully.   
 
First of all, you can't talk about this movie without talking about the special effects.  Now, the hype leading up to the movie made one think that the special effects will blow you away and it's stuff "never before seen".  In reality, the special effects are just an evolution of the effects you've seen before, just never this well done.  I think the best compliment I can give to the special effects is that it made you forget that for about 2/3 of the movie, you were watching nothing but a CG animated film.  The backgrounds and scenery is photo real, no it hyper real (because real life does not look this sweet-most of the time).  The characters animate wonderfully, and since the Na'vi are human like, not human thus avoiding the uncanny valley thing that Robert Zemeckis is fighting with in his CG movies.  These animated characters also differ from the Prequel episodes in the fact that they are real characters with emotion that act.  
 
Another great thing about the special effects is the scale.  There are several HUGE things in this movie and they are a sight to behold.  I love scenes where you see this tiny little dude next to a large set piece, and in this movie, the set piece isn't a mountain, but a giant futuristic bulldozer, or robot, or troop transport.  And unlike the prequel trilogy, everything looks real--and that's an accomplishment. 
 
Now this movie is in 3D.  When most movies do 3D (Up is an exception), it's usually a spear in your face, or a ball flying towards you.  In this movie, there is very little of that happening.  Here, the 3D is used for depth and it really is stunning.  I hope to see more movie go for this type of 3D than the "gotcha" 3D used in so many of today's films. 
 
I though the acting was well done (nothing terrible, but nothing great either) and the action was phenomenal, but as District 9 has shown, everything is better with Mechs. 
 
Now due to the hype of cost of the movie, and how long it took to make, there will plenty of haters.  And of course, this is not a "perfect" movie.  It is a bit long.  The story is a bit cliche, the acting is OK, but really none of that matters.  For a little under 3 hours, you  are transported to a totally different world that looks beautiful.  The story has heart, and there are mechs.