The ultra difficult and painfully unforgiving http://www.trueachievements.com/Super-Meat-Boy-xbox-360.htm
has been rather generous with free DLC in the past. Back in November
there was a similar update, as there was in February
This free update will add a whopping 60 levels across the Starlight, Paradise Lost, and Minneapolis worlds. The patch is supposed to be live as of now, so if you want to punish yourself, go ahead and do it.
There wasn't any patch information given, so it appears the update was simply Team Meat being generous. Because it is a free update and not paid DLC, there are no new achievements to be earned.