So I've been tooling around with iOS4, and unfortunately one of the features I use the most appears to be missing. You can't customize the behavior of the home button anymore in Settings, and as such you can't set it to do things like open phone favorites, open the camera or open the iPod controls. This is kind of a downer since I used to use the double-tap for phone favorites all the time.
I know that previous reports about iOS4 said you could double-tap and hold to bring up phone favorites but that's not working anymore, it seems.
- Holding the home button brings up voice control.
- Double-tapping brings up the multitasking/recent apps bar along the bottom.
- Double-tapping and holding does nothing.
- Triple-tapping does nothing.
- Triple-tapping and holding brings up voice control.

I know that previous reports about iOS4 said you could double-tap and hold to bring up phone favorites but that's not working anymore, it seems.
- Holding the home button brings up voice control.
- Double-tapping brings up the multitasking/recent apps bar along the bottom.
- Double-tapping and holding does nothing.
- Triple-tapping does nothing.
- Triple-tapping and holding brings up voice control.