Many experts are concerned that creatine is taken in huge doses, without much in the way of guidance. That is to say that evidence of its value and safety has yet to be ascertained. There are studies coming out almost every day, but few fail to provide definitive answers.
There is some evidence that short term use is related to kidney disease, but no evidence exists in regards to long term safety.
Theoretically, the more creatine phosphate in the muscles, the higher an athlete can perform. Supplements are meant to enhance stores of CP in the muscles.
In any case, red meat is a creatine rich food... if you are a meat-eater, you're getting it anyways.