Having watched Avatar in 3D, I thought the effect was OK, but didn't create an immersive environment or enhance the story telling; having a background in experiential design I am probably a harsher critic the most.
Should we ever have 3DTV in our house it could be an interesting experience as things (ie keys or 3D glasses), get moved and hidden by forces unexplained by Arthur C Clarke. Either that or Toddler Pangloss is being playful. I'd expect 3D without the spectacles would be like watching TV with a misaligned aerial.
Much more engaging are 3D books. Pop-books.
Baby Pangloss was given some for his birthday and they keep me amused with the ingenuity of the paper engineering. Adding this simple animation to a book is great and even more so when a character jumps right out at you.
A favourite of mine are books by Robert Sabuda. They're for older children and quite delicate so TP & BP will have to wait. Seek his books out and be prepared for magic.