I had a second-generation iBike Pro and now I use a PowerTap. It seems to me that the iBike was very accurate almost all the time. The numbers were very similar to what I'm seeing with te Powertap. The ONE exception was when topping a hill and starting a steep descent. On one 17% grade, I could pedal easy and register over 1,400 watts. Lesser downward slopes still gave odd readings, but less odd.

Everywhere else, the iBike worked very well. No calibration issues. No strange readings.

I've never used the current generation but, when used in conjunction with a Quarq/SRM/PowerTap, the Aero sounds as if it would offer data -- especially on aerodynamic efficiency -- that you can't get anywhere else. (Even a wind tunnel would be unrealistic by comparison.)