Gamestop is capitalizing on the Call of Duty/Battlefield rivalry with a cheeky trade-in promotion.
Assuming you're over eighteen and currently living in the UK, all you have to do to be eligible for the promotion is buy Battlefield 3 from Gamestop's online store before midnight October 27th, then buy Call of Duty: Modern Warfare 3 before midnight on November the 7th. Should Battlefield 3 fail to live up to your expectations, you can return it at any time up until November 18th and Gamestop will refund the money you spent on Modern Warfare 3, sans 99p.
What if you don't like Modern Warfare 3? Well, you're stuck. The deal doesn't work the other way around. Oh, and you PC gamers are out of luck too.
The promotion actually works out in Battlefield's favor. Regardless of the two shooters' endlessly-debated respective qualities, Call of Duty is a clear leader in terms of sales by quite a large margin. The promotion encourages the vast hordes of Call of Duty fans, many of which are not traditional gamers, to take a chance on the Battlefield franchise without the prospect of financial loss. This may produce some converts, or there might be some people who - and keep in mind this is merely wild speculation - purchase and enjoy both games. It also allows for all kind of doubtlessly witty quips about how 99p for Modern Warfare 3 is still too expensive. What fun.