I've used a little of this developer, and it worked fine. I don't buy the speed increase, though. If there is one over comparably dilute D76, it is negligible, as in less than 1/3 stop. At least that was the case in my system with the films I tried, TMX and TMY.
With 1+5 FX37, I rate my 100 Tmax at 100 instead of 80 for other developers and I don't think it will do any more...Evan Clarke