Excellent, fast, and easy dish -- will make time and time again.
I noticed a lot of people here, like me, aren't big fans of mustard. The recipe calls for 2 tbsp for 4 fillets (1 tbsp for 2 fillets), but you can get away with using about 1 tsp for every 2 fillets -- it'll be just enough to give the rest of the coating something to stick to and give the dish a little twang without imparting a distinct mustard flavor.
Also, I would recommending spraying the baking pan before placing the fillets on it. That way, the cheese won't fly off.