If I place my Droid into silent mode either by holding the power key and selecting Silent Mode or by pressing power key and sliding to Silent mode it will not vibrate with incoming calls or text messages. I'm pretty sure that it used to vibrate when I did this, but can't totally remember. The only way I can silence the phone and still have vibrate is by using the rocker switch on the side. Running stock Droid, by the way. Thanks!