I recently had a lesson with Brian, and I have to say that having him show me the grip and how to take it first hand, made all the difference in the world.
I didn't initially go to it, as I kept fighting the change, thinking that I needed a stronger left hand grip.
A slightly stronger grip felt much more powerful to me, although the results weren't powerful shots.
Today, in the middle of a practice round going horribly wrong, I stopped myself in the fairway on hole #5 and committed to getting the Manzella neutral grip right.
I dropped 4 balls around 100 yards, normally not a good distance for me.
I hit 2 each with my 53 & 58 wedges.
All 4 flew straight, with little curvature, and in the direction I was aligned.
On the next tee box, I hit a 265 yard drive (confirmed by Bushnell)
Dropped 3 balls, and wedged all 3 within 15 feet of the pin.
Next hole, I tattoo another drive down the middle, then push one right, but with very little curvature.
Played 5-1/2 through 8 with this grip and mishit that one pushed drive.
At that point I made a committment to myself, that I would not change from this grip again.
The grip feels less powerful, probably because I'm not strangling the club, but it produced shots that flew straighter and farther than my so called 'feelings' would have indicated.