I for one felt like i was watching some pixar animated movie whenever the Avatars would fill the screen or the flora and fauna. I heard numerous claims that this was almost photorealistic, to which i would think that the average avatard fanboy does not even know what the word photorealism means. Many of the CGI creatures showed jerkiness in their motion which indicates that they are CGI made and not even that impressively.
A lot of CGI, when combined with live footage, simply doesn't feel right, because it lacks the true depth and texture of the real objects that it is shown with. It is often distracting and it generally doesn't compare well to using 'real' things like animatronics and costume, even when they are poorly done, because they still 'catch the light' in the way that your brain expects them to.