Let's just say that old school gaming successfully made it's way into 2010/2011. Super Meat Boy is that.
The length of this game can depend on how God-like you are in the game or how crap you are. The difficulty has definitely brought more game-play hours to the game, which is what the old-school games used to have. Hard, very hard game-play. One of the reasons why certain games today have become too short is the difficulty level. Even some games on it's hardest can be beatable within a few days. Super Meat Boy however is not a game where you can finish easily in a few days (not unless you are a God-like, unholy gamer).
Some gamers may not like the game but some (or most of us) who used to enjoy old-school classics definitely appreciate the design of Super Meat Boy. The game definitely makes a clear statement that game-play is always more important than graphics.
If anyone has given negative reviews of this game, it's because they either never really played the game or were wondering why the hell is there no level-up so that they can spend points on perks and kill streaks to better themselves for the next round.