According to Business Insider's Mark Wilson, Kinect is unable to pick up some of the more subtle movements of the human body, such as wrist movement. He noticed this when playing the bowling game featured in Kinect Sports. He was told by the developers that "the game can't track spin based upon a twist of [the] wrist"--an unfortunate quirk considering its importance in the sport of bowling.
Although Kinect can do a lot of things, finer wrist movement isn't one of them--an area that both PlayStation Move and Wii MotionPlus have a leg-up on it, allowing for full bowling ball control. Of course, to be fair to Kinect, it's also the only bowling game I've seen where you can literally shot put the bowling ball down the lane, which looks hilarious, even if completely unrealistic.