ive used creatine and its effects are relatively minimal. my brother credits it with about 10 pounds for him though. the steroid use isnt only limited to the pros but also very common in college and high school. there are a lot of ways to beat drug tests. your standard bodybuilding competition like olympia and the arnold all are steroid athletes. they also have "natural" comepetitions where the competitors are tested but they use also. they just have to use different drugs.
As far as creatine, I've seen college athletes put on 15-20 pounds of muscle on creatine. But I've seen others with no response whatsoever. Depends on your chemistry, as you no doubt know.