http://examine.com/supplements/Creatine/
Scientifically speaking it is extremely safe. Its an endogenous substance that your body will easily remove excess of unless you have a kidney condition.
I cant really find evidence that a person who eats a high animal protein diet really needs much of it, and the margins of performance on it are 10-12%. Largest effects were on vegan users who are naturally low in it.
I did not gain any weight from it, but I am on a deficit so it may have just slowed me down, which scares me a bit because I am still losing ahead of schedule. I didn't do a loading protocol but I am 4 weeks in on 6-8g daily.
The secondary effect fatigue reduction is probably more beneficial than anaerobic respiration. Hard for me to say if that is just me getting used to the increased workout regime(from being a lardass) or if it is helping.
Its pretty cheap from anywhere. I got mine from ON. 200 days worth is $35.00