I bought one for my combat corvette. My home base is Trinh Terminal (Tsondama), and since the class 6 is not available there, I moseyed down to Jameson Memorial.
Put it on, flew out, and as soon as I could, hit boost. MAN! I could only boost for a few seconds, due to heat quickly rising to 97% (G5 armoured power plant), but... incredible burst of speed.
I hit a snag, however, when I tried to fly home. The route could not be plotted. Admittedly, the range has dropped from just over 17 lys to just over 7 lys... so, went to the galaxy map, clicked the option of short jumps -- no dice. No matter what I did, I could not plot a route to Tsondama.
I'm currently docked in a system 3.6 lys from Jameson Memorial, waiting for my engineered 6A FSD. I'm left wondering whether it's simply not possible to go from Tsondama to Shinrarta Dezhra with a range of 7 lys, or whether this is some kind of glitch...