I just had a chip tuned for my NSX using SR5guy's "definition" yesterday. My tuner said the definition worked great and it was obvious how much time Matt put into it. There were only two things that my tuner kind of missed in the definition: 1) access to the rpm at which the VVIS changes the volume of the intake manifold, 2) access to the rev limiter. Since I don't want to raise my rev limit above stock, point number two doesn't bother me.
Additionally, my tuner said it would have been nice if data logging had been possible in order to see exactly what cells in which map the PGM-FI is currently accessing, what signals the knock sensors are sending, etc. That doesn't have anything to do with the definition, I gather. To do that in an OBD-1 car, it seems you have to solder a new port into the PGM-FI and program something. With more modern cars, you just plug your computer into the OBD-2 port.
As it stands, using SR5guy's definition my tuner could program a chip and do dyno runs with a wideband oxygen sensor in the tailpipe. He also said that no tuner can duplicate the months of work Honda put into programming the original maps in specialized load cells, using additional sensors to collect data, etc. If you change something in the car that goes beyond the ability of the PGM-FI to compensate (like injectors with a higher flow rate), you have to tune a new chip. If you want to change the ignition timing to optimize it for a higher octane fuel, you can now do that by loading the JDM NSX ignition maps into your chip, which "SweetChuck" uploaded here on NSX Prime somewhere. Those 1994 JDM ignition maps are optimized for Japanese super premium gasoline which, from what I have heard, legally had to have an octane rating of at least 96 RON but usually had closer to 100 RON.