IPA file support prerequisites?

I have an in-house iPhone app. Developed about a year and a half ago. Up until now, I'd ship it to users as an ZIP-archived app bundle, instructing them to unzip, add to iTunes library and sync.

Now, there's this fancy new IPA file format that simplifies this process considerably. Question - what are the prerequisites for its support? Does it require a specific version of iOS or iTunes? I开发者_StackOverflowf yes, which version?

Preempting the questions - yes, we do support over-the-air installation. iTunes-based installation has to stay for the sake of remaining iOS 3.x users.

---

It shouldn't, as:

1. An IPA file is merely a ZIP file with a different extension
2. iTunes has been using IPA files for apps since the App Store first launched