"Silent" bug fixed in 10.1!
Switching from Normal to Vibrate only will remain locked until you go into the Notification settings and change vibrate to Silent (or anything else). Pressing volume down all the way will take you from Normal volume down to Vibrate. You will no longer be able to go lower than Vibrate to Silent with the hardware volume down key.
This was a huge fix for me as my phone would go into Silent without me knowing it far too often and I would miss VERY important calls/emails/texts.