Hi,
In quite a similar way to powerlifters I'd imagine. I cannot speak for the majority of powerlifters, but I'd say that it is generally acceptable to suggest that a majority of powerlifters do not train to failure - they train to peak. That said, they gets heaps and heaps stronger.
Referring back to my example of EZ curls.
Point A: 110lbs x 10 reps x 1 set (last rep is a cheat rep)
Point B: 135 x 8 reps x 4 sets (absolutely no reps were taken to concentric failure)
I'd say that this is a very successful case of progressive overload. If it's not then the end desire was still achieved at any rate: quality muscle gain. I let my body dictate progression and did not try to force it too much.
I fully appreciate what Pitbull and others are saying. Looking at Pitbull's avatar, clearly, going to failure is definately working for him.
However, for a lot of lifters, in my experience, going to failure is detrimental. That's not an excuse for someone to cruise through a workout though; you've got to be true to yourself and get to a point where you know that you're 1-2 reps shy of true concentric failure.
For me, going to true concentric failure led to nothing but disappointment, frustration, pain, and in a state of constant lethargy. Not going to failure has led to increased emergy, increased motivation and, above all, constant gains.
I don't think that this is a one size fit all game.
All I'm saying is if you're smashing your tits off in the gym, and everything else is in order, and you're still not gaining, try backing off the failure training and let your body dictate progression rather than forcing it.
True- mix things up.