The verdict is great, but based on limited information as there just aren't many curvy roads near me. I expect to really get a feel in the mountains this fall.
What I do know from my mostly suburban driving (with a couple of curvy blasts) is below. The caveat is that while the Coupe and the Speedster (and your D) share the new front suspensions and steering, the rear suspensions are different. Check with Carey for specifics.
- The steering is very direct with little play but a bit heavier, probably due to a quicker ratio.
- The ride is not as smooth as the Speedster. It's not at all punishing, but it's more focused. Carey may have made mine a bit more focused than the norm since he knew I wanted to see what it would do on the track. I know my motor mounts are harder than what he plans as normal. That gorgeous exhaust treatment unfortunately had the pipes hitting against the body at times with the softer mounts. Because of that the NVH levels in my car are a little higher than what most folks will experience.
- The balance of the car feels much better. In the Speedster you could feel the inherently unbalanced nature of the car. Mine was 39% front/61% rear in weight distribution. You don't feel that with the mid-engine Coupe. It feels very balanced at the 6/10s I've been able to drive it and I really want to get it on some scales to see what the weight distribution is. Of course this will be moot to some point in the Speedster/D since they'll be rear-engine, but the improved suspension will mitigate some of that.
- Another thing you don't feel is body roll. Even without stabilizer bars I haven't experienced any lean. I'm sure there is some, but you just don't notice it.
- The suspension - at least in the configuration on my car - is a bit noisy in the rear. I have some ideas on how to mitigate that a bit, but should be moot to those of you getting the new Speedster setup as it will be different.
While not the suspension, the brakes deserve mention. I am not sure exactly what is used on the rear, which is the same on all cars, but I have the Wilwood upgrade in front. Being non-power they require a firm press, but they inspire confidence.
For those of you getting the mid-engine Coupe, you can scroll past the shifter discussions from now on. Carey and crew have nailed it. It's surprisingly crisp and precise for a remote linkage, with a very mechanical feel. Oh, and the 5-speed is great. It'll pull strongly from 1800 rpm in 5th, 50 mph is just a bit over 2000 rpm. I've got 427 miles on the car and filled it up once - unnecessarily, I found out. The gauge read less than 1/2 tank so I thought I'd fill it up. Remember, it's a whopping 22 gallons. I only put in 9.5 gallons. DOH! I expect a tank to last at least a month in local driving - less, of course, when on the road or pushing it hard. On average I should be able to go between 650 and 750 miles on a tank. 
Ok, I'll keep going. The A/C is able to keep it comfortable even in the ridiculous heat we've had lately. It's not like a "real" car made by a company with billions in research budget, but it's pretty darned effective. The car got caught out in a downpour about 10 days ago while parked, and the only water that came in was a drop or two in the trunk (the one in the back 
) that leaked in around the screws holding the grills on. I've since applied a bit of clear silicon to them, which should solve the problem.
The power to weight ratio is about 10.3 lb/hp, which is pretty darned good. It feels very good 
. The power just keeps coming in all gears. I really cannot imagine why you'd want more in this, but I'm sure I could be convinced .
I'm still tweaking here and there on mostly OCD-related stuff. I plan to get a PPF put on it soon, and then I won't be so paranoid about driving on the highway.
Woohoo!!