Late 1970's through the 1990's Whispertone series were the high point of Kenmore vacuum quality. It has been down hill from there. That is a good durable vacuum, though it was the beginning of Kenmore trying to push more air through single stage fans using smaller motors turning higher speeds, though it is a pretty decent Lamb motor. The Whimpertone was still pretty conservative that way compared to what would come out later using cheap Chinese motors.
That Panasonic made Powermate is still the state of the art today and is very popular with central vacuum system sold under a variety of names like Hayden Deluxe, Nutone and Centec. A lot of vacuum makers try but none have come up with a better powered brush. Kenmore still gave you real, adult sized tools then, not the kids toys you find on more recent Kenmores.
I grew up around Kenmores too. Many collectors sniff at them as just a department store vac, but compared to the mega buck high zoot Electrolux carpet torpedo I bought recently at the Salvation Army, I don't think Electrolux or Aerus Lux can even begin to justify their high prices based on quality and good design. A Whimpertone like yours is a better vac in every way IMHO. I would compare it favorably to any canister vac I've seen from Sebo or Miele as well. I laugh when salesmen like to point out their adjustable suction, varying motor speed to change suction, something i like to point out my parents old 1982 vintage Kenmore 4.1 has, in addtion to that adjustable opening at the hose end. Vacuums in general have lost so much quality over the past two decades that it is to the point where a good vac from 20-30 years ago is a better vac than the mose expensive new vacs on the market today. It is sad when you think about it.
Keep that old Whimpertone. Take it apart, sanitize it inside and out, put some elbow grease into the finish, polishing it and waxing it to a nice luster. That vac won't let you down.