I've got a D-Jetro on my R32. After the installation the car gained more power over the std ecu. I guess that be attributed to the fact that the D-Jetro was tuned to the car and the std one had a std shitty map in it. The fuel economy was better by miles. I could get over 500k's to a tank with sensible driving round town.
Hyperdrive in Perth installed and tuned the car. It retains the six throttle setup but had I put the Apexi kit on it as the afms were now gone.
All in all I like the way the car drives and runs, the response is great. I've had no problems at all with it. There's always going to be arguments over which one is better but I would happily put another D-Jetro on another GTR.
Best bet is to find someone that has one in their car and get them to take you for a drive.
Jon