beware, if you don't have a beta software authorized console this type of thing may cause you to get banned from xbox live.
I have one of these myself.
Edit: I understand the download is for the non beta version, but if it is a code exclusively for members who received the preview disk, it could possibly be setup similarly. I find it strange you wouldn't just take it to a game exchange place next time you go to buy a new game? (the one you bought, I mean)