I've had a couple of sessions on the K2, and its super nice. Can get foiling as soon as you've got enough wind to pull yourself onto the board (for me that's about 7mph with my 17m beast), and is very stall resistant once you're going. I find i can foil through situations which my previous board would have dropped off the foil every time, such as downlooping a gybe in 7mph when your kite goes slack as you bear downwind - I wouldn't even attempt that before.
I've got a 128 Sunburner which is a cracking size, i've not detected any flex in it, gives a very reliable connection to the foil. The scoop on the deckpad is really nice to keep your feet where the y should be too!
The K2 foil is very user-friendly, but the real USP is the neutral foot pressure.
I've taken to windsurf-foiling this summer, cos I like a bit of a challenge, and found that really a lot of fun; you need a great deal more wind than kitefoiling but the experience is wholly different. When kitefoiling, your kite is up there doing its thing, and you're often down below being at times quite brutal with your foot pressure to stop your foil from firing itself out of the water; it feels like a battle sometimes.
Windsurf-foiling is entirely different, there's no fight, only balance. Small changes to your body and rig are all that's needed to control the pitch of the foil... its hard, yet rewarding, as when you get it right it feels more like flying thank kitefoiling does.
The reason for this is foot pressure, you don't feel like flying when 70% of your bodyweight is on your front foot trying to tame a beast.
Now the K2 doesnt feel like windfoiling, but what it does have is neutral foot pressure, which doesn't seem to alter much when your speed increases. I'm an engineer at heart and I don't understand how it works the way it does; you'd think that must be the case on all foils, but somehow it isn't.
In short (yes, i've rambled on sorry!) its a far more enjoyable foil to be on than any other i've tried, easy, fast, stable and much less of a fight against the board at speed and in gusts. For me its rewriting the rulebook of what I can get away with doing, it seems very pitch stable, and i'm sure I'd be doing foiling manouevers on it if i removed the straps, but i'm currently trying to get comfortable using them for foiling jumps and tricks
Hope this helps!