I think it's safe to say that no dyno is perfect - I don't think anybody will argue that point. I think what's important is that the tests are repeatable and consistent and to some degree at least standardized.
For the consumer, what is important is to be able to look at dyno data and compare different motors and brands to be able to make a more-or-less educated purchase decision. I think that has a lot to do with the popularity of some dynos over others. One dyno may be better but if it's not in widespread use it's hard for a consumer to make an apples-to-apples comparison.
For the tuner, the dyno (whichever one a person prefers) is a tool to get the most out of a motor and compare results to sort the good from the bad. You can't do the job without one in my opinion. A track MAY be a better test but I don't know any person, car, track, weather conditions, tires or batteries are THAT consistent.... Besides, you can't get the track to print a sticker that you can slap on the motor.
