I have used it(gen II). I have also owned a PT, PTSL and Quarq. The ibike did quite well if I were solo training on nice roads and were trying to hold the power, i.e. 2x20's. But once I moved from hoods to drops, sat up to climb or started group rides, it was quite a ways off. Now I did only borrow it for a week, but that is all I needed to make me want a "true" power measuring device.