The effects were awesome, but the plot was kind of standard and predictable. There are actually a bunch of funny discussions online about that if you search for them. To me it was a lot like Cameron's other movies, predictable with some lucky main characters and a few others killed off to prove a situation is serious.
It also would have helped me if I couldn't identify some of the plants in the background of shots as very obvious earth plants. I saw it both in 3-D and standard, and the 3-D seems to just be distracting from the effects. The 3-D also has that tendency to make things shiny with I found irritating. Let me note that I vehemently hate 3-D as a medium anyway. Here it is 3 bucks extra for any 3-D movie, so no wonder Avatar is making so much money.
As to being depressed it's over, Why? It is a MOVIE, and not really a ground-breaking one at that.
--Mia