I use them all the time, but found out recently that a regulator is needed for 6.0v with this servo. I fried one and JR repair said it was over voltage that caused it. I added the Duralite 5.1 regulator(s) to my 6.0 v packs and all is well again.
PS-it took a while for the servo to fry, so it would probably be OK for a while, but might quit at the wrong moment. -Mike Oberst