STEP UP 3 is by far the best of the three films. John Chu is really developing as a director. Unfortunately, the first act is so poorly written that I doubt many people will make it through the whole film. The film has its share of weaknesses. Shot for 3D, the 2D version of the film looks like all the backgrounds are green screen plates, although they probably are not. Most of the dance sequences are clearly shot on a soundstage, and the lighting is bright and flat, which probably makes the 3D look better. In fact this is one of those rare films that probably looked better in 3D, although some of the shots were clearly gimmicky, with things (and people) flying towards the camera.
Much of the film feels like a slightly better episode of Degrassi or Melrose Place, but the dance sequences really rise above the mediocrity of the script. If you like dance, you might enjoy fast-forwarding to the dance sequences in this film.