The computer effects were probably the best Hollywood has ever produced in terms of the machines and robots as well as the actual world itself, the smurf lookalikes still didn't look totally convincing though in the way they moved. The human eye is very perceptive over things like this.
The film itself was epic and spectacular, but was more of a spectacle and an event than a fantastic film, I felt a bit sleepy in the middle! (this might have been down to the 3D,as the glasses seem to make the screen a bit darker, and the 3D is hard work on the eyes).
As for the 3D itself, its still evolving technology and I think it works far better on animations rather than real lift stuff - it just didn't look that convincing during this movie.