I agree with both of you - it will provide your muscles with more energy, allowing you to push yourself further and hopefully, through that, make more substantial gains in size and strength (providing you're eating right and drinking gallons of water).
Also, as abear mentioned, some people, whether it is because they have high natural levels of ATP or creatine or due to a handful of other factors, just don't respond to it (i'm one of them).
Another effect is water-retention within the muscles. I've never wholly understood how or why this is achievved, but creatine leads, more often than not, to more water being stored in your muscles which can make them look bigger.
And finally, use the search button up the top there, creatine's probably one of the most covered topics in these forums.