We need to seal a few door frames a bit better! But aside from that they're very good for solar gain, even in this weather, and stay toasty warm compared to a "normal" house.
I've never had my thermostat above 17 degress and even with this cold weather it is more than warm enough in the house. Add to that, we are always in credit when the energy bills are due so there's no complaints from me there. Very pleasing really :)