This game does not translate well to the screen size of the iPhone. Im sure if I had an iPad it would be much easier to play but currently the game leaves much to be desired. It can be difficult to determine where a connection can be formed with other goo simply because my finger obscures parts of the screen. The goo moves around on the structures in a unpredictable manner that means 1/2 the time I end up whipping the camera around instead of picking up and dragging a goo where I want it to be. Its easy to zoom in an remedy some of this but to do so sacrifices the ability to see exactly where your objective is, which means your building blindly in a game where building strategy is the most important thing. I remember this game coming out on the PC on steam to some critical acclaim. Im sure it plays much better on a computer or iPad, but steer clear if youre using an iPhone. Maybe the iPhone 5 has some better luck.
Something that might remedy this for taller puzzles is allowing portrait orientation? On the height puzzles I feel like this would be very beneficial.
Brohloff about World of Goo for iPhone