viewing experience. There were no "gimmicks" of things flying at you, it was done very subtly.
This is how I like 3D being done. The Martian landscape and everything was very nice in 3D, but I wasn't watching the movie going "Holy cow!! That 3D was awesome!" It was just part of the movie.
I had no regrets paying for it; however, if you require in-your-face 3D so you can feel like you got your money's worth, then this flick is not it.