Just had a quick skim through this thread... wow a lot of different views and opinions. i also wanted to give my 2 cents regarding the Hub vs Roller dyno (eg, Dynapack vs DD) debate based on my experience.
firstly this statement - all chassis dynos are designed to give an 'accurate as possible' indication of engine power/torque. with that said, it should be realised that actual engine power is one thing, being able to measure is though a chassis dyno of some sort is another. Other than the actual force applied at the load cell, approximations are used.
very clearly the Hub dyno is the winner for consistency and repeatability, although in most cases generally will read 10-15% higher compared to a Roller dyno simply because they do not have to deal with the additional drivetrain losses (wheels/tyres) and friction between the tyre and roller. These figures vary so much from car to car that there is no way to compensate for it, so it is literally ignored on a Hub dyno, with 10-15% being the approximate. Note that i did say 'in most cases' as it is possible for the additional drivetrain and friction losses to be negligible, which is why the software doesn't make its own assumptions.
On a Roller dyno, ramping up cars in different gears can sometimes yield different results, but this indicates sometimes large fluctuations in friction/slip at the roller as the tractive effort increases/decreases. A car that also 'climbs' the front roller will usually read a higher figure, as there is less rolling resistence and friction at the tyre as it is no longer riding on the back roller. A Roller dyno relies on consistent strapping/chocking, climbing, tyre pressure, tyre compound, gear selection, etc, to get good accuracy and repeatability - obviously all of these variables are eliminated in a Hub dyno.
In summary i can say that Hub dynos DO read 10-15% higher most of the time and can have better consistency/repeatibility compared to Roller dynos, although it is not all that hard for the Roller dyno operator to ensure the same consistency/repeatibility on ANY car if they are paying attention, meaning a lot of the time it comes down to the individual operator/tuner. The more experience a tuner has, the less of an issue this usually becomes.
As for this R34 making over 1000hp... completely accurate or not, it should be in the vicinity of 1000hp based on the information in this thread.