You can quickly pause anything playing in the iPod mode of the iPhone without any button presses. In fact you don't even have to remove the phone from your pocket. Just unplug the headphone jack. Apple was clever enough to realize that if your headphones come unplugged, most likely you don't want your music to keep playing. You gotta love the attention to detail. I've tried this with both the headphones that ship with the iPhone and the traditional iPod headphones.