The movie was great. Don't expect it to be a remake of the original. It has a great twist and current findings of mythology were used. Medusa's true story was told compared what was said in the original clash of the titans. As for 3D, it was hardly seen. Save your money and watch in 2D. The experience will be the same and no headaches from the glasses.
As others have said, typical story line. The main focus was the action and the CG characters. The 3D makes it worth wild. Must see it in 3D, don't think the regular version will do it justice.