Iron Geek,
It helps you get a feel for heavier weights that you wouldn't normally be able to handle. Adds 10% to your bench so it doesn't overload too much. Maybe it primes the CNS. Definitely helps lockout as there is no help at the top. One good thing is it keeps your elbows in tight for good form and takes stress off your shoulders. I've got the blue and the yellow versions. I would skip the blue and go straight to the yellow higher support version if you are around 315 already.
I've used a few tools to increase my bench. I also have chains which improve lockout, and I also built devices that allow you to overload the eccentric portion and the weights drop off at the bottom making the concentric portion lighter. I've also tried using board devices that limit the downward ROM but personally never found much use for them.
But really, if you want a big bench, you need to be a big man. Seemed to me that every pound I put on added a few pounds to my bench. I stopped at around 225 on my 5'10 frame because my wife said I was getting square looking like Spongebob