If Apple and Android had a separate search/install/purchase experience based around demoing games and unlocking the full version, I would buy so much more then I currently do.
http://www.androidauthority.com/how-to-get-refund-apps-googl...
Also, compare with Kindle, where you can download a sample of any book you like, and it just sits until you get around to reading it. Once you finish the sample, you can decide whether to buy it. I think that model is closer to free with in-app purchases than anything else.
[1] https://support.google.com/googleplay/answer/2479637?hl=en