3D gives me a headache. The only time it didn't was with the new Tron, because it was very subtle. My other complaint, is that they tell your eyes where to look. You can't take in the scenery during a conversation because it's out of focus and looks better when looking dead center.
However, kids love the 3D, and if I didn't have the headache problems I would love 3D movies a lot more. Most 3D movies come with the basic version as well, so if someone comes over and doesn't enjoy 3D you can always pop in the regular movie. It's all about what you prefer and how much you watch tv if the extra cost is worth it. They are fun to show off!