I've had one kite foil session on the Axis ART799.
First impressions, it has an extreme initial lift then it will stall quickly if you don't quickly level the foil. The initial lift is the quickest I've experienced on any foil and will surprise a lot of people, it's definitely for advanced riders. The 899 and 999 which I also ride (wing only) have a more gradual lift.
Once up, the 799 accelerates crazy fast and slices through the water, it's very efficient. I rode it with the 350p stab so the whole setup was quite a change from my usual 700/380 setup.
It turns well, but not as well as the 700 I felt. High aspect wings need a different turning technique too; you need to initiate the carve by pushing on the toes of the forward foot and put pressure on the back leg too. Difficult to explain, it feels like riding a plate which you have to skids into the turn.
Will the 799 replace my 700 ? Not necessarily, I enjoy how easy and forgiving the 700 is. If I want more speed and/or glide then I'll use the 799.
And the 350p stab is great, very loose

I did notice the fitting isn't perfect too...