Battlefield 3 Premium Content on Xbox 360, have I been screwed?

There is a slip of paper in the inside cover of the game case with your premium code.  You must redeem that in order to be premium and if it's missing go back to the store and tell them that it is not there since they need to provide you with one if it's a brand new game.  If it was a pre-owned copy of the game then you will have to still buy premium.

After you redeem the Premium code and your Premium file downloads to your console make sure that you restart BF3 so the game initializes with the Premium file present.  When you get to the main title screen you will receive a pop up stating you are now premium and you will have a Premium background.  Next you will have to download the DLC expansions covered by Premium (the file just gives you access to download them but doesn't download them for you) via the Premium tab of the BF3 in game store (not via the Xbox Live Marketplace or it will charge you money again)then close BF3.  After all 5 expansions completely download (this could take a while since each expansion is about 2 GB) start BF3.  At the main menu you will receive a series of pop ups stating that you now have each expansion.  Now from the main menu go to multiplayer, open server browser and then open the server browser filter by clicking R3 and check all new maps and game modes or you won't find any games on the new expansions.