I myself have not used one, but I know several people who have, including the new model. Some of these people were happy with them initially, but long-term they all became frustrated with them and abandoned them.
IF you are very careful to calibrate it correctly, AND stay on top of the calibration when conditions, equipment, etc. change, and you mostly ride in the same position, and don't do any sprinting, then sure, it seems to be generally almost accurate. Otherwise, if you are like most people, you don't stay on top of if it, you don't recalibrate it when you change things, and you end up like FordFasterr, claiming ridiculous numbers on some thread on the internet...
You can take a PowerTap wheel or SRM or Quarq, and swap them between bikes and not worry about recalibrating, just a simple zeroing at the start of a ride, and verification of the calibration from time to time.