On my iPhone 4 I have to click the home button a good 3 or 4 times to get it to work, EVERY time. It's driving me up a wall.
That's what happened with my iPhone 4, and why I decided it was time to replace it. I got it right at launch, and I really was hard on it, though. Going to the 4s was a good compromise, because they are cheap right now LOL
My hubby had his iPhone 4 in a Griffin Defender case and his home button worked just fine.
LOVE the back button! I want one! And an LED notification...