When using an iPad with the bluetooth keyboard, the ESC key acts as the home button. On my iPhone 4, the ESC key will wake the unit from sleep or bring up the passcode lock screen but it will not act as the home button in any other scenario (leaving an app, going to spotlight search on the home screen, or bringing up the fast app switching bar). It's kind of an annoyance. Especially when you want to use fast app switching to copy something from a text to an email message. I'd much rather use the keyboard than the device's home button in that scenario especially when it's sitting in the dock...it is simply faster with the keyboard mapped home button.
Is this a bug in the iOS 4 BT keyboard support or a "feature?" hah.