If you are looking for a way to use VJ software sync video elements to music for a live show or a rock video check out ArKaos VJ. The software not only responds to MIDI, but also supports ReWire so that you sequence video elements from inside your primary music application ( ex. Ableton Live, FL Studio, Reason...).
If you are familiar with sequencing with software you'll find ArKaos VJ easy to use as it offers a drag-and-drop keyboard interface right within the software. Simply import pictures and movies, drag stills of videos to a key, then drag an effect to the key. Pressing the keyboard within the application using your mouse or sending MIDI data to the application via a hardware controller or from a ReWire host launches the clip.
Flash movies with editable text and live video camera feeds can also be used from within the application. There are plenty of effects to choose from, and you can customize effect parameters. Beat detection is also included. In addition to using this live, you can also export your work to a Quicktime movie.
For me, the only downside was the pricing model . The software runs on both PC and MAC and costs $335 / 279€. While I think this price is more than fair if you are primarily a VJ, I wish they offered an alternative and somewhat stripped down ReWire version for people who are primarily musicians who want to add video elements to their live shows or create rock videos for YouTube.