As with most pieces of miracle technology in fiction, it has a horrible downside. Spock speculates that it would destroy any life in the area of its effect. David confirms that it could be perverted into a terrible weapon. Khan learned of the project from a mind-controlled Pavel Checkov and added stealing the device to his objectives in addition to seeking revenge on Admiral Kirk. The devastating potential become a subject of great controversy in the quadrant, with the Klingons doing everything from launching protests against the project to trying to steal it for themselves in Star Trek III: The Search For Spock.
Revenge and new birthMutara nebula, destroying the Reliant. The device forms a new planet, named "Genesis" and the system is subsequently quarantined because of the previously mentioned controversy. However, the planet proves unstable and eventually destroys itself. David Marcus is killed by the Klingons trying to steal the secrets of the device and the knowledge behind the technology is lost as a result.
In the versus debate
Trekkies see this device as an ultimate weapon in the Trek universe. In their eyes it could destroy entire fleets of enemy starships. Some have gone so far as to calculate exorbitant energy figures for the collapse of the nebula into a planet. These calculations are completely backwards as the collapse of matter into a planet is a net negative energy event.