All you iPhone developers out there better check your email inboxes because Apple Corporation has just released iPhone OS beta 3. If you want to update, just keep in mind that there's no turning back because your iPhone cannot be downgraded to an earlier version of the OS.

In any case, here's the changelog in the email. It's pretty vague, so we can't tell you exactly what's been changed. Apple really has a knack for doing this to us, doesn't it? Oh well:

iPhone OS 2.1 beta 3 is now available and is to be used for testing only. View the Pre-Installation Advisory for iPhone OS 2.1 beta 3, Readme, and Release Notes before installing the new versions of the iPhone OS and SDK. As a reminder, pre-release software is Confidential Information and is subject to the terms outlined in your Registered iPhone Developer Terms and Conditions with Apple.

Apps developed for this OS beta version cannot be submitted to the App store, so just make sure that you're ready to update when you do.

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