Ok, this has indeed grown on me quite a bit. Its cute, like Cut the Rope, but the physics of it seem a bit more predictable, and there are no reflexes/timing ones I've come across yet, so it feels a little less trial and error then Cut the Rope, but similarly a polished, attractive and engaging puzzle game. Clearly, there is a bit more to it then cut the rope, as if you really try to think about the physics of the construction you are rewarded with better scores and can work to the "OCD" score for each level.
Still though, I have to admit I'm in the $4.99 may be a bit much camp. Not in the scheme of the world where 4.99 is less then a movie or a book, but in the scheme of comparison to other good puzzle games that are .99 or 1.99.
A better rewind mechanism, a counter of free goo balls & some way to see how your score on each level compares to OCD would be great adds. If they are there, I havent seen them yet -- just finishing first chapter now.