As with every feature there is the risk of people using it wrongly. But generally, In-App Billing is a great feature which allows me to offer services without having to flood the Play Store with a second, pay-to-buy app... If you don't want to pay for an app you think that's worth it, then just don't... I personally don't have a problem doing so, because I know how much time is spent developing apps... so why not honor this?
What concerns me more are apps that put advertisements in Notifications or anything alike... but I wouldn't keep those on my phone...
But back to topic: Thank you, +Android Developers
for making this much easier now!