Following from my rant about ringer volume...
it appears the volume control buttons still work when the device is locked so its easy to change volume setting in your pocket.

Just to make this more fun, the volume setting graphic can be inconsistent... if you turn the volume down with the device locked, the lock screen indicates full volume, but the settings page shows ringer set to silent.

I also somehow managed to get locked out of the lock screen, despite knowing my code. Reboot fixed that though.