These work well for small quantities of moist food. For larger quanitites they have no advantage over conventional cooking methods. Vegetables cooked in the microwave can retain higher levels of vitamins than boiled vegetables. Large items of foods can retain cold spots in the microwave and need to stand until the heat is conducted evenly throughout. A microwave oven temperature probe ( not a glass thermometer ) can be used to check that the temperature is high enough in the thickest part of the food.