I wish I was surprised, but this seems to happen with a lot of OS-extending apps on the iOS device. I've never heard of a game being banned from the app store, but as soon as it's something that Apple doesn't already have baked into the operating system...
It's been said before and it'll be said again: Playing in Apple's walled garden isn't a safe way to make a living.
I think it's more fair to say that making things that should/could be OS features isn't a safe way to make a living. Or if you do want to risk it, just be aware that you should have a fallback plan.
Just started using OS X heavily at work on a large monitor and started to notice a bit of a window clutter problem. Your app looks like it could be the ticket!
How is a to-do app "should/could be OS features?" Or a camera app that uses the volume button? Or Instapaper?
I don't think there is an obvious way to tell what Apple has in their roadmap. Specially when they publicly downplay the importance of some features only to implement them later. Maybe they should make their roadmap public? :)
In many cases I think it boils down to "we reject your app because not only we have thought about this use case already but we have a solution in the works, and while it's not ready yet it will probably blow anything else you would have thought about because we know the system in and out, so your app would be dead a few months from now anyway. As you're doing an impressive work on it maybe you can join us to contribute on that work we're doing right now, or be patient about it and concentrate on other areas." In other cases it's probably overzealous employees.
I noticed Apple hate was growing in line with their price history [1] and I understand there will always be baseless haters, but it appeared to really blow out of proportion during last week.
It's not only not a good idea to use private APIs, if you do so you've failed. You're a bad developer. It's like writing file handling code that assumes all operations always succeed. There's a reason private APIs are private. They will change. Your app will crash. It's not a matter of if, it's a matter of when.
Yeah, I mean stories like this shouldn't really discourage developers.
Number one: if you are a developer and you don't plan for something like this that's just a lack of awareness on your part.
Which leads to number two: don't depend on a single revenue stream. You're making decent money with your first app? Cool, now pay a couple of interns to handle support requests and start working on the next one.
It's been said before and it'll be said again: Playing in Apple's walled garden isn't a safe way to make a living.