That discount brings the post-rebate price of the device down to a palatable $149.99. Buyer beware: when we checked the source link at T-Mobile.com, we couldn't find the same image that included the promo code. But if they give you any guff, a quick call to their customer service should convince them to give you the same discount.
The $150 price nearly matches Walmart's in-store price of $148.88. However, the discount from T-Mobile's website requires that you are a new customer. Let us know: did you get a discount on your new Sensation 4G?
source: T-Mobile via TmoNews