It should clean as well, if not better than a D 80. Make sure the brush roll is a 4 row brush roll,(4 rows clean better than 2, and also makes the Kirby easier to push) make sure there is a new belt installed,or at least one that is not worn down, and make sure that the brush roll is adjusted correctly. The bristles of the brush roll should protrude slightly from the bottom of the rug plate. Also make sure that the rug nozzle itself is adjusted correctly for your carpet by turning on the Kirby with the rug nozzle in the highest position (foot pedal all the way down), then step on the adjustment pedal one click at a time until you hear a change in tone of the Kirby motor.
This indicates the correct setting.
If the Kirby is hard to push at this setting, go back up one.
If the suction is broken when you push and pull the Kirby at this setting go down one notch.
Also make sure the Kirby bag is empty, or at least not jammed up.