Thank you for sharing your thoughts too Juhani.
1) This design was inspired by a game that took a similar approach and which I really enjoyed. The first time I finished it I used Tapjoy to unlock some content, the second time I did it without. I hope our users will have a similar enjoyable experience in our game.
2) What I had in mind when creating this feature was that some levels can be very hard to beat. So what we want to offer is an alternative which is also hard, but maybe preferred by the user.
I understand your point of view. Maybe we will chose a different path for our next title, but the future will show. Maybe we can have a chat about that on the next Android meetup too.
Best regards (from Japan),