I've bought the first spindle I came across in some cheesy electronic store. The guy only had "Platinum" discs. They looked very cheapo, but it was at the end of the day and I really wanted to try SSBB that night.
Well, it turned out those disc were pretty good, as I have not encountered one single error or lock up.
The game is INCREDIBLY AWESOME!!!! I already love it just as much as Mario Galaxy