IIRC the Limbo team grew over time, it shows in gameplay, the second half feels less personal and more like a generic platformer. They hired more people to get done with it. It don't mean it is rushed, but to me, the second half lacks personality compared to the first half.

Also, I don't like the idea of using gameplay time as a value statement. Maybe I say that because I don't have money problems, but I find that the tendency certain gamers have of judging games in terms of dollars per hour of gameplay is pretty damaging, as it incentivizes developers to focus on gameplay time more than polish. 3-10 hours is already plenty for that style of game. Note that there are many AAA games in the 10 hour range.