Games For Windows now offers the Gun Sonata DLC for the Windows edition of Bulletstorm (thanks BeyondUnreal). Here's what they say, including an odd console reference:

Download the new Bulletstorm 'Gun Sonata' DLC pack and gain access to 2 new Echoes maps: Guns of Stygia and Crash Site as well as 3 new Anarchy maps: Hotel Elysium, Villa and Sewers. As if that wasn't enough you'll also be able to use the Flamingo and Pulp leash variants to ensure you're looking good whilst racking up the skillshots! There are no refunds for this item. For more information, see www.xbox.com/live/accounts.