I've been on the ARC for about 3 weeks. Like all D3 skis I have tried I was comfortable riding it from the first set. It turns awesome for me and gets me earlier consistently across course. My percentage at -35 is higher on this ski, and although I haven't conquered -38 yet, I'm getting more attempts at it than on any other ski I've tried.
The Helix H2 worked really well for me too, but the ARC turns more consistently in my opinion. Prior to the H2 I was on the Vapor (green). I think my best on all 3 skis was close to the same, but I couldn't get consistency on the Green vapor. My old bag of tricks just didn't work on that ski, so I wasn't able to scramble back into passes after a mistake.
I'm running stock settings and binding position so far, although I had my from binder loosen up and go way forward on me at one point. Ski felt far less smooth, but I ran right up into 38, fixed it between sets and did the same in my second set (felt much better though) after a binding move of 1/2" or more. Great reminder to check my gear more often, but also how forgiving D3's are for me.