Apple 现在要求应用程序开发人员提交针对 2.2.1 但也为 3.0 构建的应用程序。我（我想大多数小型/兼职开发人员）只有一部 iPhone，并且由于升级到 3.0 是不可逆转的，我想就在过渡期间最小化风险的一些最佳实践提出一些想法.
我知道在这两种操作系统上进行全面回归测试没有万无一失的方法，但是任何关于如何最小化回归的想法都会有所帮助。
这是Apple的确切文本：
今年夏天，数以百万计的 iPhone 和 iPod touch 用户将转向 iPhone OS 3.0。从今天开始，所有提交到 App Store 的内容都将在 iPhone OS 3.0 的最新测试版上进行审核。如果您的应用提交与 iPhone OS 3.0 不兼容，将不会被批准。
App Store 中的现有应用程序应该已经在 iPhone OS 3.0 上运行而无需修改，但您应该使用 iPhone OS 3.0 测试现有应用程序以确保不存在兼容性问题。在 iPhone OS 3.0 可供客户使用后，任何与 iPhone OS 3.0 不兼容的应用程序都可能会从 App Store 中删除。
You really can't test on a device against both 2.21 and 3.0 unless you have two devices. If that's really important, you can think about an iPod Touch (assuming your app doesn't require an iPhone).
As far as the simulator, once you install the 3.0 sdk you won't be able to build targeting 2.2.1 any longer. The old 2.2.1 build target gets replaced by a 3.0 target. To support both, you should think about building a virtual machine that retains the 2.2.1 sdk.
However, I agree with Alex... not much need to think about supporting both platforms. 3.0 is solid, and it's clear from today's Apple mail that it's now the major focus, as far as testing & compatibility.
Edit 5/17/09: One thing I learned after this post is that on the Mac, you can't virtualize the Leopard client OS. Apple only allows you to run the server version of OS X in a virtual machine. IMHO, this really limits software developers as a group, among others, and I hope this is changed eventually.
您对将手机从 2.2.1 升级到 3.0 有什么顾虑？最新的修订版似乎或多或少是可靠的。
我在 iPhone Dev Central 上看到了可能有用的这个文档：技术说明 TN2246