Bad: Your cockerel might go through a hormonal idiot stage as he grows up. He might not outgrow it.
Ugly: He might terrorize the pullets by wanting to mate ALL THE TIME to the point that they will hide anywhere they can get away from his unwanted attentions.
Good: He may grow to be a total gentleman, taking care of his ladies. He may sire wonderful, healthy chicks. He might be the most beautiful chicken in your flock.
Toss-up: He might crow a lot. You might like this. Your neighbors might not.
Another toss-up: he will eat a lot of food and not give you any eggs (if that's the main reason why you have chickens).
The only reason you NEED a rooster is to have fertile eggs to hatch chicks.