Man I hate them, they are like a DLC, which has ruined the gaming for me. In concept, it's good, you download one app and then buy books or whatever, however most of the developers just abuse it and what you'd get otherwise for free included with the app now you have to pay for when they nickel and dime you. I never rate an app with in-app purchases more than 3 stars. UNLESS! It's justified, like a book store and you pay for different content from different authors.