So I know it's a little late, but if you're trying to just have it vibrate for everything, you could turn the notification sounds back on and flip the switch to silent. If you want it to ring and vibrate for calls, but just vibrate for notification you could use a silent ringtone (an audio file with nothing but silence) for notifications.
I have a problem with my new 4S I got recently. I use my phone as my alarm clock and when I was using my older iPhone (3) I could set my alarm, lower the volume all the way down and flip the vibrate button on the side of the phone and it worked like a charm. Now with the new 4S, I do the same steps to set my alarm and am awoken in the morning by not only by the vibration of the phone on my night table but also an alarm sound, it is at the lowest possible volume but at 5:00am when everyone else is sleeping that alarm is loud - I've tried the notification none option but then it doesn't vibrate. Any advice on getting this to work on the 4S?