Crazy Machines is a good game that'll keep you entertained for hours (if you don't follow a walkthrough ;) ).
My opinion: I think that this is a great game for those who like logic puzzles. It is the game that I play the most on my iPod Touch (I also have Sims 3 and Theseus right now) and it is very enjoyable. When you'll get far into the game, you'll have to think a lot in order to solve the different contraptions. The game is quite long and isn't cheaply made like the other contraption game available from the App Store.
I am enjoying the experience of playing this game. The game is interesting and the controls, flawless. Even if the game is in 2D, it looks great and is esthetically appealing.
*Note: There is another version named Crazy Machines Action which is more recent (and it's the same price). It looks like it has all of the features of Crazy Machines (and some new ones), but I am not sure. So check it out!
So I'm going to let you go with this:
GET IT!