Effect is fairly minimal....but it still has an effect. Before it used to be mega expensive and simply not worth it.(Like 5 years ago).
Now, its reasonably priced, so I'm not really against it.
I usually take 5g/day. The loading phase often talked about in magazines is pure BS btw. It was a scam used to seel more creatine to people.
You do have to keep welll hydrated though while on creatine, as if you don't you might experience some cramps. Thats about it though. Its a very benign supplement.