I have one on my TT bike with a SRAM crank set and red rings 53/39 and another set of rings 54/44. And I have one on my road bike with a SRAM 50/34 crankset. I use my Garmin 705 on both bikes. Before the Quarq on my new Cervelo, I had a PT. I found the power measurement about the same when I changed over to the Quarq.
I was an early adopter of the PM and my wife has the same set up on her TT bike and road bike. We have sent both of those PM back to Quarq for service and the customer service was excellent. Contrast that to my PT where the Saris customer services as okay but not great. Quarq sent a power meter to me IN ADVANCE to me sending the one needed repair so that I would not be without a PM.
Whatever you can do, or dream you can, begin it. Boldness has genius, power and magic in it. - Johann Wolfgang von Goethe, writer