Cabin now Further in the Woods, in 2 Ways

Joss Whedon's upcoming horror flick, Cabin in the Woods, has been pushed back almost a year. It will now premiere January 14, 2011. The studio, MGM, says they are postponing the film because early response to it has been strong, and they want to convert it to 3D. The second half of that sentence makes me feel uneasy. Has there ever been a 3D horror movie that was actually good, rather than kitschy?