Has anyone here used an air admittance valve. I've read what I could find
but would like to hear from someone that has actually used one.

I'm removing the wall above our kitchen sink and would either have to
install an air admittance valve or reroute the vent and a loop vent isn't an
option here. The reroute would require elbow the vent and run it six feet
to a wall, up to the attic, then six feet back over to the vent stack.