Usually the microwave doesn't produce very good results. The mechanism behind how it heats food is to blame. High energy radiation (microwave) is shot into the food and it causes water molecules to start spinning. The friction in the spinning water translates to heat. It's not recommended for most dishes; however, there is one crucial benefit it holds over the oven or stove...
Heat from a pan or oven enters through the surface of the food and has to conduct to the center. It takes longer and it's hard to tell what's going on inside. You can roast a chicken and it looks beautiful on the outside, but the inside is still raw because of this. Microwaves penetrate much deeper before it is converted to heat. In a microwave there is much more heat originating in the center of the food rather than just the surface.
However, microwaves work high intensity in a short period of time. This rapid process means possible uneven heating. One area could receive more microwaves and heat up much more, you may have to rotate the food halfway.
Practical application: If you are in a rush and bring out chicken that is still raw inside (or the steak is just too rare for you), stick it in the microwave. It cooks the center much faster than sticking it in the oven or stove. Another benefit is that it cooks the center quicker without overcooking the outside like direct heat could. This saved me many times when I thought the chicken was fully cooked and served it.