I have a set of D2's. The comfort and performance is based on how you set them. Tire choice also plays a big role in the comfort.
My car currently has all of the springs set to stock pre-load. The height is set to 1cm of wheel gap in the front, 1.5cm of wheel gap in the rear. I keep the dampening 5 settings from the softest up front and 1 setting from the most stiff in the rear.
The ride is very nice and my performance is great, but my car is not very low. I have 225/50/16 on the car so it is almost stock height.
One very important thing to know about d2/ksport coilovers for the b14 is that the rears will blow once your start messing with the preload on the spring or when you start slamming the car.