There’s a great reason for iPhone users to upgrade to the new iOS 4.0.1, and it’s not the changes to the signal strength indicators: it’s the reversion of the behavior of the wake/sleep button.
There are two principal complaints users are making about the iPhone 4: the loss of signal when you bridge the antenna with your salt-water hands, and the oversensitivity of the proximity sensor (aka the “I keep hanging up on you with my cheek” problem). I’ve found the antenna issue to match the conventional wisdom, and have had far fewer dropped calls on the iPhone 4 than on any previous model. The proximity sensor, though, has been a real problem, as I’ve been hanging up, accidentally muting calls, and starting FaceTime calls – no matter how much I think I’m holding the handset away from my cheek at a weird angle.
Of course, I used to press buttons accidentally on previous versions, especially when I would put the phone in my pocket and wear my handset. In every version of the iPhone and iOS before 4, this was easy to avoid: pressing the wake/sleep button during a call would lock the phone. So I’d press the button as I put the phone in my pocket.
In iOS 4.0, that behavior changed: pressing the wake/sleep button during a call would hang up the call. So for the first week, I’d try to avoid the accidental hangup problem by pressing the wake/sleep button, and so then I’d hang up on them anyway. This was a clear change in behavior that I haven’t seen documented anywhere. (I don’t know if it behaved the same way on the 3G or 3GS.)
In iOS 4.0.1, the behavior is reverted – pressing wake/sleep locks the phone again. So now, if you make “always lock when you start the call” part of your muscle memory, you won’t hang up on people quite as often. And if that isn’t what you want from your phone, what is?
UPDATE: It turns out that I was entirely wrong – Elan Lee had a larger array of phones to test than I did, and he determined that the behavior didn’t actually change – it’s just that the wake/sleep button only locks the phone when your headset is in. Since I’d never had the cheek problem before, I wasn’t locking the phone when I held it to my ear – that hangs up in earlier models as well.
I did hear from a few other folks thanking me for telling them about the locking-with-headset trick, though, so my doofusness wasn’t entirely useless.