Pros: controllable power, sleek, tremendous on serves, good all-court racquet
Cons: more stability on off-center hits would be desirable
My current racquet, the PB7 packs a powerful punch while providing a substantial amount of control. I've hit more aces and unreturned serves than ever, yet the 107 inch string bed is within the range (upper end mind you) used by pros (such as Agassi). The frame has a conventional width, yet still manages to produce ferocious power. A "tweener" is one that tries to have a good blend of both power and control, FYI.
Currently, I am using it in a 5.0 league. Although I rely much on consistency, when I step up to unleash an offensive shot, the power is there in spades. It is more controllable and "aimable" than the larger racquet I used previously. My placement has improved significantly since making the switch.
I wish the racquet were a bit more stable and forgiving on off-center hits. It is not as good in that respect as say the Prince EXO3 (100 inch for example), David Ferrer's racquet. However, I've had my share of benefit due to the irregular shots (which can mess up the opponent) produced at times when they are off-center. I don't try to hit off-center; of course I'm not advocating for using anything other than the sweet spot.
The racquet is well-balanced, especially after putting in one segment of weight adding tape to the inside middle of the top of the racquet. That much tape makes it almost exactly balanced, neither head heavy nor head light.
For players with very fast swing speeds, this racquet may be tougher to control. Thus, I don't expect Roger Federer to use it any time soon. The bulk of the touring pros nowadays use "deader" racquets than the PB7 because they can generate all the power they need with their incredible swing velocities.
I tend to string it on the high end of the range. The high end of the recommended range is 60; I have both of mine strung at 58 pounds. I use RPM blast on my primary, and a very thin gauge Luxilon on my backup currently.
So far, *knock on wood*, I'm undefeated in the 5.0 league with this racquet. While no racquet can substitute for skill and technique, having a suitable stick can augment, amplify and aid one to play better. For me, after play testing a bunch of racquets, my weapon of choice is the Volkl PB7. Thanks to the owner of Go Pro Tennis, Nils, for recommending it to me.