Presumably There'll Be More Face Kicking In Bulletstorm's DLC.

Entitled, Gun Sonata, it features three new maps for the Anarchy multiplayer campaign: the Sewers of Stygia, the ruins of Hotel Elysium, and the Villa. The DLC also includes a couple of new Echoes maps, which are Bulletstorm's equivalent of time-trials.

The pack will run you $9.99 / £7.99 when it releases in the Spring. Before you all start moaning about the announcement, note the Spring release date. It's also worth remembering that while a game's going through QA, the rest of the team are left twiddling their thumbs, meaning they have time to design and build additional content like this. No, it should not have been on the disc.