Those who participated in the Lumia 900 feedback study that saw Nokia publish a survey and offer $50 Amazon gift cards as an incentive have reported that they've begun receiving said rewards. Should you have completed the required number of surveys and are eligible for the gift card reward, you will be contacted soon enough.
Our George Ponder has confirmed this acknowledgement and has also been alerted to his $50 gift card redemption code.
Let us know in the comments when you receive yours. What will you be using the card for? You can also join in the discussion on our Windows Phone forum.