Excellent food! The apple/fennel/bitter greens/pecan/smoky blue salad and the lamb sliders were worth the trip all on their own. Two of the three desserts we tried (the chocolate pot de creme and the red wine and quince sorbet) were spectacular, and the third (pumpkin cheesecake) was perfectly serviceable.
The pasta with mushrooms and lemon sauce was delicious beyond words. The bouillabaisse, however, was a disappointment -- one of the mussels didn't open, and the sauce tasted quite frankly like they had opened a can of tomatoes and dumped it into the pan.
The only other flaw was the portion size, which left me hungry at the end of the meal. However, I suspect that's a problem most diners won't face: I'm 6'8" and I avoid gluten (thus, no bread to pad out the meal).
I will eat at Lark again -- but I'll most likely wait until the next Seattle Restaurant Week makes it more affordable.