Second outing with the blade v8 18x20 yesterday, and this is my impression:
* Like everyone said, V8 is a little lighter and more maneuverable, and it is easier to swing than V7.
* The feel of V8 is a little firmer, direct, and clean than V7 which was super plush and muted to me.
* V8 is not at all unstable, but due to its mass and tip heaviness, V7 feels more stable to me, and it produces heavier penetrating flat balls.
* V8 seems to have more spin potential due to its lower swingweight, and overall it is more versatile than V7 to me.
* V8 is less powerful to me than V7, and the power from V7 comes mainly from the mass of the head.
* V8 produces really nice backhand slice, and it is a little easier to lift up low balls than V7 can.
If you like weight, plow-though, plush feel, and rock solid stability, I think V7 is the one.
If you like maneuverability, spin-potential, firmer feel, and versatility, I think V8 is the one.
I will hit again tomorrow and report it back to you.