So, during the Steam Summer Sale 2011, Super Meat Boy was updated and has a new achievement: "Medium Well". It's description is only, "Spend as little time in hell as possible"
How do I earn this new achievement?
Unless I messed up with my calculator, the A+'s for each level in hell put you at a time total of 631.8 seconds.
Update: Super Meat Boy was later updated in 2011-07-20 and what was originally the "Medium Rare" achievement has now been renamed to "Medium Well".