Yes. It's worth the 3D.
This isn't the usual 3D film where the 3D is used for surprise pop out moments. The 3D is used to add depth and create space. There a couple of moments where the 3D is used incredibly effectively to reenforce the vertigo the main character is experiencing. Fabulous use of 3D.
Not sure what the target audience is though. It feels like a kids film, but our son was bored silly. My wife and I enjoyed the film, but even we felt it dragged at times.