I though Avatar used it brilliantly; and it really pushed the limits of what can be done. At several points in the film I felt that if i reached out I would be able to touch the items on screen; and I;m not just talking about the floating ash or tiny creatures of Pandora. Some of the more reality-grounded scenes in the military base were as convincing if not more so in their use of 3D than some Padora scenes.
However, Alice in Wonderland and Clash of the Titans were both disappointing for me - by and large I thought that everything was flat, but staggered, so we had Alice and the Mad Hatter (flat) a few feet in front of a few trees (flat) a few feet in front of some other things (again, flat). It wasn't the immersive expereince that Avatar was; I think that Alice and Clash were both filmed in 2D and then converted into 3D and I didn't really see the benefit in this.
However, I won't totally write-off D just yet. I think Tin Tin is being shot using the same equipment as Avatar and so I will be very interested to see how that turns out. I just think at the moment it might be too expensive to do 3D to the standard Cameron pioneered for all films, but with time this will become more routine.
I still dream of the day when it's proper holographic 3D though like the recordings seen throughout Star Wars, such as when the Jedi communicate with one another or when R2D2 plays the messge from Leia in A New Hope.