Paul & I use the Indi dyno. We don't know what the numbers mean, or whether they're real, but it does serve to compare one motor to another or different set-ups on the same motor.
We have some Monster numbers, both amps and RPM on Monster stock motors on our Indi dyno. They were fast motors on the track.
We've also had some motors dyno poorly that went well on the track.
Use the numbers for comparison only. If you change springs, or brushes, or both, the Indi will tell you whether it's better or worse. The Indi will tell you if one motor's turning more or less RPM than another, and whether one motor's drawing more or less amps than another. If we've got two motors, and one's going in a truck and the other in a buggy, the Indi helps us choose.
We never compare numbers from our Indi to numbers from any other dyno, and never compare our motors to someone else's based on any dyno numbers. As Aaron says, only the track can tell for sure.
Engineering Without Fear