There's also Apple's continued refusal to allow devleopers to have separate pricing for updates vs new purchases. It's either a free update to the existing app,

There's also Apple's continued refusal to allow devleopers to have separate pricing for updates vs new purchases. It's either a free update to the existing app, or it's an entirely new app listing with the same price for new users and people who owned the previous one. I've seen this circumvented by creating a package deal of the old and new versions, which then gets discounted via the "you already own part of this set" mechanism, but it's a messy experience and not something that many developers have done.