Well, if you haven't gotten yours, you're going to need a new option going forward.
From ZDNet:
.... Microsoft has stopped accepting new registrations for its free Custom Domains service, effective immediately. The move was announced today on the Windows Live Admin Center page, where users manage custom email addresses.
According to Mike Schackwitz, Principal Group Program Manager for the Outlook.com service, Microsoft will “wind down the Custom Domains product” while continuing to support existing custom email addresses “indefinitely.” The service has been in existence since 2005.
The move matches one that archrival Google made in December 2012, when it closed its Google Apps Free Edition. (That service had been in existence since 2006.) Today, Google Apps for Business costs $50 per user per year, with extra charges for enterprise features such as email archiving.
Microsoft’s goal is to move its customers to paid products, including the $60-a-year Office 365 Small Business (which includes Exchange Online, SharePoint Online, and Lync Online) and the $150-a-year Office 365 Small Business Premium (which adds a license to install the Office desktop programs and mobile apps for business use). According to a company spokesperson, existing customers will get a promotional offer.
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and further down in the article:
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Although the service no longer allows you to assign a new custom domain to Outlook.com, administrators of currently enrolled domains can continue to add and remove existing addresses for approximately two more months. On a yet-to-be-determined date in June, administrators will lose the ability to create new addresses in the administrative control panel, and existing custom addresses will become standalong Outlook.com accounts, using the same custom address but managed individually by signing to the Outlook.com interface.
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With that being said, those using this option may need to be looking towards other services.