I bought the black Electrolux UltraSilencer Green way back in 2010 - it’s essentially a similar machine to the Harmony with a different carpet nozzle.
The UltraSilencer was highly rated by Consumer Reports for air flow through the hose and bare floor cleaning and for filtration and noise control. The Dust Magnet combination carpet/bare floor nozzle is quite amazing and effective and easy to use…it’s got a “swinging” suction chamber facing the carpet and a pair of grey soft ultrafibre bristles for bare floors. The dust bag and hepa exhaust filter are very easy to change. The hose is really long and it’s a pleasure to use and there is a clip on the hose handle to store the famous “butterfly” upholstery nozzle/dusting brush.
My only gripe: there is no where to store the crevice tool onboard. Except for that, it is an excellent suction only canister cleaner!