They're running some cross-game promotion with Mass Effect 3. Completing the demo for this will unlock stuff in ME3, and completing the demo for ME3 will unlock stuff in this. The "stuff" is in-game items such as weapons and armour.
Anyone played the demo yet?
If it was anything like the Gears of War 3 beta which gave you unlocks in the retail game then definitely do not delete the game save . But then this is EA so I wouldn't remove anything until the game is released and you have acquired all your unlocks.