I have an app that I was going to release as a free (lite) version with some of the total functionality and a paid full version with advanced functionality. Now, with in app purchase for free apps I am thinking of going that route with the ability to unlock features as needed. I'm not talking about a trial version that expires.I want people to be able to try out the app and get an idea of the interface and functionality before deciding to purchase the full functionality of each major section of the app, basically.

Here's an analogy of what my app would be like. Let's say you have a cooking app that teaches you to cook in different styles. There could be major section for French, Italian, and Chinese. Each section could have some rudiments unlocked in the free app so users can see the UI and basics of the functionality. Then, the user could decide to purchase each major section (or not) individually with in app purchase or buy the full versioned app (with the free/paid model).

One concern I have with offering a free app with in app purchase would be with feedback. I would be very clear in my description in the app store that there is in app purchase for full features but I'm worried that less serious users could/would leave negative feedback. I suppose that's always a risk but curious about any experience with this.

It also seems that it could be a whole lot more complicated keeping track of what portions of the app are locked and unlocked with in app purchase. I know I'd have to have all the code for the full functionality and "lock" the portions that haven't been purchased. How do people usually lock portions of their code? I'm not talking about the process of purchasing (I've read the In App Purchase Programming Guide) but after the purchase has been made. Would I just keep track of what the user has purchased and put conditionals on the sections that are initially locked? Or is there another way to do this as well?

My instinct is for the in app purchase (particularly since users could purchase the major sections that they want individually).