You don't need to test on every iPhone OS device though. Just the ones with different hardware changes. So basically: original iPhone and, iPod Touch 2G, iPhone

You don't need to test on every iPhone OS device though. Just the ones with different hardware changes. So basically: original iPhone and, iPod Touch 2G, iPhone 3GS and iPad. And this hardware combination (or 3 of the 4) isn't hard to imagine. Not for a US-based developer, at least.