Publish your app(s) to the Windows Store and/or Windows Phone Store between December 20, 2012-February 28, 2013 to qualify for the following rewards:
If you do not already have a Windows Store or Windows Phone Store account, follow these steps to obtain one:
All new subscribers who are not part of DreamSpark, BizSpark, or MSDN and publish an app during the entry period are eligible for a subscription reimbursement in the form of a Gift Card ($49 for Windows Store or $99 for Windows Phone Store). To request your gift card(s), visit www.generationapp.com/ultimateexperience and check the box for "Request a Reimbursement."
You may request a reimbursement at any time between December 20, 2012 and February 28, 2013 once your app has been published. This offer is only good in the 50 United States and D.C. to legal residents 18+ who meet the contest eligibility requirements and are not current Windows Store or Windows Phone Store account holders as of December 20, 2012. Limit one (1) Windows Store and one (1) Windows Phone Store reimbursement per Publisher GUID. This offer is non-transferable and cannot be combined with any other offer. This offer will be fulfilled in the form of a Gift Card and is not redeemable for cash. Taxes, if any, are the sole responsibility of the recipient. Each reimbursement will be associated with the Publisher GUID used to sign up for each Store. This offer is good up to the first $60,000 in reimbursements or until the end of the promotion period, whichever comes first.
More detail here.