With their rapidfire capabilities, cruisers are extremely effective at eliminating the Light Fighter and Rocket Launcherfodder. In addition they are excellent as fast strike ships, especially if their Impulse Drive have been upgraded to a reasonable level. This can be especially useful if you're trying to intercept a returning fleet that has been spotted on a Sensor Phalanx.
Uses and Advantages
The Cruiser should be used to clear off the large numbers of Fodder around a fleet so damage from your fleet's much larger ships will be able to take out the meat of an opposing fleet. A Cruiser can take out an average of 6 Light Fighters or 10 Rocket Launchers a round, making it invaluable for this purpose. As has also been mentioned, its great speed and reasonable cargo capacity make it a useful raiding craft especially in the early game.
Although fast, they do not have anything like the punch a Battleship can deliver and, as such, should not be used as frontline strike craft in the later game. The Cruiser also needs to have 3 more levels of weapons technology than the Defending player's shielding technology in order to damage a Deathstar.
With the development of the heavy laser and the ion cannon, light and heavy fighters encountered an alarmingly high number of defeats that increased with each raid. Despite many modifications, weapons strength and armour changes, it could not be increased fast enough to effectively counter these new defensive measures. Therefore, it was decided to build a new class of ship that combined more armor and more firepower. As a result of years of research and development, the Cruiser was born.
Cruisers are armored almost three times of that of the heavy fighters, and possess more than twice the firepower of any combat ship in existence. They also possess speeds that far surpassed any spacecraft ever made. For almost a century, cruisers dominated the universe. However, with the development of Gauss cannons and plasma turrets, their predominance ended. They are still used today against fighter groups, but not as predominantly as before.