On BlackFriday Week last year I finally pulled the trigger on an DOF H6 with the smooth gearbox motors:
Had a bit of sqeeking and clacking noises from some of the motor assemblies, but of them were gone after checking all the screws/bolts that hold the joints.
Took three afternoons to build up and get going. And another 2 weeks to tune in the movement to my liking and get rid of most of the noises. Also had to replace the flimsy USB cables to the controll boxes, as they gave me problems with the connection.
Otherwise I’m happy now with it.