I develop for Android and iOS too, and Android Market is terrible with declined purchases and "failed to deliver" issues. What's worse is that there is no good way to get information about what's wrong and who's affected. In-app purchases also have terrible bugs on Android - bugs like this http://code.google.com/p/marketbilling/issues/detail?id=14 open for months cause payments to just 'disappear'. The only thing worse than Android Market bugs is Android Market support. There is no way to get Google's attention, and emails to support come back with useless, auto-reply messages. I spend at least 30 minutes a day fiddling with refunds and fixing things up for users who contact us about problems. It is infuriating - I'm embarrassed for Google.
I haven't had a single bad payment experience with iOS.
So, I'm about to take the plunge into the market, and have been wondering about this exact issue. How do you deal with it when you get failed to deliver problems? I mean, you probably can't just give them the apk, that's its own can of worms... any tips?
I haven't had a single bad payment experience with iOS.