I basically have a device rotation that basically works like this: I have the current iPhone. I keep it updated to the latest stable and it's my primary devel

I basically have a device rotation that basically works like this: I have the current iPhone. I keep it updated to the latest stable and it's my primary development device. When significant new beta comes out, I buy a latest gen iPod Touch and install the beta. This becomes my primary development device for all beta builds. Once the new iOS version is released, I update my iPhone to the latest OS version. At the same time, since Apple allows some overlap, I downgrade the iPod Touch to the latest old version of iOS. At this point, I leave the iPod touch frozen at that iOS version and use it for old compatibility testing.