I am using Pioneer Dura Ace 9100 on My Madone. When I bought my first one, it had hadware failure on my second ride. But they changed it immediately. I bought it via Clevertraining.com. Since then not a single issue. Batteries are easy to change. It requires calibration before every ride as most of other power meters but readings are perfect. The only down side is, you cannot exchange between bikes.
I am so happy with it. I am even thinking to buy second one for my second bike.