I've been ridding a 65" Z7 ST for the past two years ( I'm 5 10, 155). I tried a 66" and 65" Fusion a week ago and immediately felt smoother and more stable on the Fusion. Comparing the 65" Fusion to the 65" Z7 ST, I would say that the Fusion was a bit more stable, better through the edge change than the Z7 ST, and just as fast. The 66" didn't turn my onside quite as well, but was turning my offside really really well with stock fin settings. I shallowed up the fin on the 66" and decided to go with it. I had 4 tournament rounds on it this weekend and topped my best score for the last 4 years on it (3 @39) and equaled my best scores from the last few years (2.5 @ 39). I had one bad round but that may have been due to some adult beverages being consumed the night before.
Overall I'd say the Fusion is a great ski. I was all over that ski at 38 a couple times and didn't go in the water. I would bet that I would have been in the drink on my 65 Z7 ST.