Have had this for 5 months now.  When we purchased the unit, there was a loud 60hz hum that could be heard when the oven was turned off or at certain times while running.  GE indicated that WE would be responsible for hiring separately to remove the oven.  Then they would replace parts.  And we would again have to hire separately to re-install the oven. (We live 15 minutes outside a major city).  The hum is still there.