Yes compared to a flexible wing. I measured maximum values of about 2.5-3 for the coefficient of lift, and 3.3 for the coefficient of pull by using steelyards (see the video) with wind speeds of 10 m/s and 12 m/s of a 0.11 m diameter and 0.5 m span Sharp rotor.
No compared to High lift coefficient and biplane kite which can achieve a value of 3 or 4 with far less drag. But I think the management of Sharp rotors is easier and we can build some structures with them: they are like bars.
Some stacked flexible wings seem to show a loss of efficiency when stacked with low spacing.
I put three 0.11 x 0.5 or 0.6 Sharp rotors with 0.2 m spacing under a kite: the pull was strong (60-70 N) if we take into account that the three rotors cover only 0.175 m², flying at about 20 m/s (wind speed 8-10 m/s), the pull of the kite being only about 10 N with the rotors, and 30 N (a low value, but I chose a low performance kite on purpose) when it flew alone. I have not see a major difference with 0.41 m spacing, video from 1:16. I confirmed this more or less today. But more accurate tests with different sizes of Sharp rotors would be required.