I found Mentzer-style HIT training was not as good as I had hoped because it lacked functional, practical movements. The whole 4 seconds positive, 2 seconds hold, 4 seconds negative thing gives an insane burn, but I prefer a more "standard" method when handling weight. I lost a lot of strength doing HIT training because the slow reps forced me to drop the weight significantly, therefore disabling me from performing heavy lifts.
I feel that Mentzer-style HIT training has its place in a training regimen, but it should only be used periodically to change things up -- never as a permanent foundation for a bodybuilding routine.
However, training WITH high intensity (i.e. going to positive failure) I feel is absolutely vital to achieving optimum workouts and muscle development. Of course it is necessary to adjust rep ranges, set numbers, exercises, rest days, etc. as your personal experience dictates. Everyone is different -- finding what works best for you through adjustments such as the ones aforementioned is key!