Instead of painting all in-app purchases with the same brush, let’s call the problem by name: Nagware. (“Pay to win” is also acceptable.)
Even then, though, it is hard for me to get too worked up about it. While the nagware model might be making Rovio (e.g.) more money, they’re getting less of my money than they used to. Yet I still get to enjoy their games.
The funniest bit to me is where they want me to pay or take a break from playing. For me, that’s a feature. I need a reminder to take a break. I’ve stayed up way too late playing Angry Birds several times. Why would I pay to eliminate a feature?