Love mine. I have them on my Corsa, my GS Trike, but not on my Giro. I can ride all three without noticing a difference - unless I pay attention, then I really like the Q rings. When I first got them, and they were only on the Corsa, I really noticed an improvement in my knees, the smoother spin and a slight increase in Avg speed on my commutes to work (14 to 14.25 mph).
But, a few years down the road and I don't notice the difference between the Corsa with and the Giro without them anymore. Not sure why not, 'cept I commute on the Giro and ride the Corsa on road rides (faster), so maybe it's the different purpose for the 2 bikes.