I've been very injury-plagued in my running career. Usually I get hurt early in the track season. Training will be going great then I'll come away from a race with especially sore calves or weird foot pain or something along those lines and things will spiral.
I think it was dumb for shoe companies to assume that making spikes as light and flimsy as possible was a good idea. I've just never been able to prep my legs for the beating they take racing in e.g., Nike Victory. Being able to actually train in the Dragonfly has been a game-changer. I'll still have dead legs post-race, but not the acute muscle/tendon pain that seems to precipitate injuries.
It feels to me like the most significant aspect of the performance boost is that my "little" muscles are prepped for race intensity since I've trained and stressed them in workouts before I toe the line. Seems a logical development in shoe technology that companies would start making racing shoes that you could also practice in, hence allowing you to practice more effectively for your races.