I first discovered this type of workout with 10X program. And, you know, I decided to try it at the gym and I wasn't very impressed. As I already used to go to the gym and as a gym-goer, I found that I was getting new results, I was pushing myself to new limits. I was working my way up and then slowly working my way down with my negatives and that actually gave me a lot more functionality, and a lot more endurance, in my workouts. This gave me that extra push, and I highly recommend it.
Regarding my results so far: one of my biggest hobbies is - I'm a mountaineer. So it helped me out a lot with rock climbing specifically for my functionality my strength, in my endurance especially.