Have you tried building a iOS landscape-only application without the support of UINavigationController?
It's super-simple on versions >=3.2, but on 3.1.x, it's a pain.
The problem manifests when creating a new view in the AppDelegate and adding it as a subview to the UIWindow of the application.
On iOS 3.1, I need to manually rotate it around 90 degrees to fix it. Here is the code for the (not-perfect) fix:
This fix particularly doesn't work when the user holds the device in portrait mode. I've tried creating a fix for all orientations, but gave up after many many frustrating hours. The rotation of the new view will almost guaranteed be wrong when the user holds the device in a not-landscape position. (This can even be "laying flat on a table
It's just a mess... Please everyone, please upgrade to 4.0 or newer.
Oh, and if you're a developer and have any comments to this, please drop them here or send me an email to firstname.lastname@example.org.