As Dave and John said,it is a great tool for gauging the effects of changes made. Don't get too hung up on trying to compare your numbers to someone else's
I own a Superflow engine dyno but before I bought it I looked at all of them.
The Stuska numbers will be different than the same setup on a Superflow. The modern Stuska setup is very repeatable and user friendly because it does not force the engine to accelerate at a determined rate controlled by the computer software . Instead,it accelerates at a rate dependant on the power of the engine,and the software converts the data into what it "should"be at the desired rate. A lot of manipulation goes on to make it seem very repeatable.
This is not a dig at anybody else's setup,just my take on it. I prefer to use a setup that controls the acceleration rate by a servo controller and does less manipulation
Any dyno is only as good as the guy running it and how accurately and often he calibrated it.
Keith