For only 200 pts it might be worth it for the chance to practice flying the helicopter without pissing off the rest of your team during multiplayer. Otherwise, I'd pass.
It's pretty standard to not allow refunds on gift cards but what's shady about the Wal-Mart preorder is that they're emailing and charging you for the gift card immediately and not when the game ships. They're basically locking in the preorder now. I guess you might be able to fight for a refund...
I sent a PM to Amazon about this but I also submitted a question to their cust. service about my existing Portal 2 preorder. I got a standard "we don't offer gift card price matches" reply but they did give me a $10 promotional credit as a one-time exception.