I'm using Xubuntu which has XFCE as DE. And it's possible to switch users fast with hotkeys, without locking them. Hotkey is Ctrl+Alt+F7 (F8, F9, F10, F11).
Pulseaudio works isolated with each user so sounds are not mixed and it's good.
But bluetooth has an issue there: when you connecting to already paired bluetooth device it can be connected to ANOTHER logged user. How you can check it? Profiles will not be available when you click right mouse in bluetooth-manager applet.