So here's the deal, I downloaded the Guitar Hero iPhone app a few months back onto my iPhone 4, and I was doing REALLY badly on it. I thought to myself.. "wow, i suck" but then I began to notice that I was only losing points whenever I had to hold down two notes at once! the iPhone seems to not register the two fingers straight away, causing a delay between the initial press to the screen reaction! So anyway, I left it for a while thinking it was just a bug within the app, but then I got an iPad for my birthday and it installed the app on there, so I thought i'd try it out and guess what, no latency issues! I've since tried various other apps on the iPhone 4 and there is definitely an issue with the multi-touch. When attempting to use the 'guitarist' app, if I pressed to fingers on the screen at once, there'd be a delay between initial press and sound, and when 3 or more fingers were pressed.. well, i got absolutely nothing. I'd really appreciate it if you could take the time to check your iPhones to see if you have similar issues as I have searched around on the web, and have only seen one post discussing it on the apple website discussion board.