With the addition of fork cartridge kits in the past few years, I have not seen a dramatic reduction in the lap records at tracks that would lead me to believe that the kits ability to necessarily lower lap times for an individual.
It might allow one to clean things up on track, but that's still back to an individual's tuning or your track side tuner, which few have.
Chassis development is still back to springs and geometry for the real baseline to develop faster laps. Sometimes, the installation process results in changes that alter the static or operating geometry that one might not recognize.
It's not the Holy Grail.
In some Japanese motorcycles, the manufacturers have done some pretty exotic things in materials and in development that have cost them dearly. To keep prices down, and recognizing that hard core racers aren't going to leave things alone, some bikes are coming with some pretty crummy fork internals. So, I think the kits are here to stay.
I've been on a couple Triumphs on track, and I think there biggest problem is geometry.
Good luck with your decision!