On the code side you have to run your own backend purchase server because there is a ton of subscription information that is only relayed to the server (Cancellations, upgrades, downgrades, cross grades, billing problems, etc.), as the app has no way to know directly (Until SK2.) Services like RevenueCat help small devs deal with this, but then you have another cut out of your paycheck.
Things like price testing require more backend setup because Apple offers no way for an app to grab product information from themselves (You have to know every identifier, there is no way to just request "all available IAPs" via StoreKit.)
So basically, there is a ton of room for improvement on the dev side, and a lot of easy wins for someone like Stripe to capitalize on.
As a user, I don't have many complaints, other than not having an easy way to request a refund, other than finding the App Store email address and pleading your case. It should be something you can do via your purchases screen directly. As a dev, not being able to issue customer refunds sucks, as many users will think you are dismissing them by saying, "You've got to ask apple for a refund."
I’ll frequently not buy from sites that want registration and card info because of the hassle.
I’ll probably end up using things I already have accounts with (amazon, Google, steam) but will never buy from apps that require me to sign up with them to buy stuff. I already hate registering with companies to play games.
Basically I'd expect successful competitors with Apple to be companies which do the same. Abusive companies aren't going to be popular but I suspect Stripe, Shopify, Amazon, etc. could convince a fair number of people that they're no worse on that regard and better in some other way.
My worry with the "anti-steering" requirement being removed is that every company will redirect me back to their own website with their own payment system, and I'll have to manage all of them individually, or phone up their call center to try and get anything cancelled.
Easy to avoid by not subscribing to anything, but every app seems to be trending that way.
Any iOS devs care to weigh in? Apple's system could just as easily be a godawful mess. No personal experience but I've seen people online complaining about how StoreKit sucks.
They've had in-app purchases since 2009 and no competitive pressure from other SDKs, because they can block them with app store policy instead of needing to offer a better product. That sounds like an easy environment for it to become an afterthought; the people using it have no choice in the matter if they want to be on the App Store.