creatine does work...but not for everyone. there are so many different varieties of creatine though. you cant go and believe what the manufacturers say, you need to talk to people that have tried it.
the most common creatine we see nowadays is the good old creatine monohydrate and the newer creatine delivery system formulas (cellmass, cell-tech etc).
if creatine works for you, you notice it straight away. within the first couple of weeks you should see typical weight gain. if you don't see results in your first 6 week cycle then it probably won't work for you, and you might need to try a different form of creatine.
basically...
creatine monohydrate: good old stuff, pure creatine, cheap, if it works for you the results will be quite good.
creatine formulas: creatine mixed with glucose, nitric oxide and other stuff. can be very expensive, seems to work well for people.
best stick with brand names tho, you pay for what you get