Recent 3D films like Beowulf or Toy Story 3D made your eyes ache a bit - the 3D in Avatar was more subtle for the most part. The CGI was top-notch. Things moved as you'd expect, including all materials.
Cinema is safe. Home reproduction was getting to the point that it wasn't necessarily worth going to the cinema much any more; you could just wait for the DVD or Blu-Ray. With 3D, there's a good reason to see films in the cinema again - at least, in my opinion.
And Avatar - what an epic film. A good story, well told. Go and see it.