I have to admit, I was seriously disappointed by the way the age-revert system worked. I understand that the monstrosities people became is supposedly their fetal/placental forms, but with the same amount of mass as they have now, but it's still absolutely retarded. First of all, the 'equivalent mass' bullshit doesn't play a part in putting a can back together, or fixing stairs. It's just an obvious attempt to make the game seem more presentable, since people would have issues with killing babies.
Except I wouldn't have an issue with killing babies. First of all, it's a game; you're already killing things. Just because that thing happens to be younger now doesn't change the fact that you're going to kill it. Besides, what about Dante's Inferno, or even Silent Hill? Sure, they were demonic babies for the most part, but they were still babies.
All that, and the incredibly shitty attempt at a plot twist really disappointed me. The puzzles weren't as good as I'd hoped, either, though that's possibly since I've pretty much seen everything you can do with time puzzles thanks to Braid and PoP. Either way, I agree with Yahtzee: an attempt to be three different games, and being shittier than all of them. See also: Spore.