Of the four concerns mentioned, three are questionable factors.
Leaching of toxins from plastic and other containers is less a function of the microwave and more a function of the container. If we heat foods in containers made of questionable compounds in the oven or stove, the same issues persist.
Extremely hot food temperatures? How many people have burned themselves on things heated on the stove or in the oven more often than from the microwave? Our guess is a lot more.
Admittedly, we should question the structural changes of foods heated in a microwave, but if the consequences of such changes are unknown, then we can't really say they're negative yet, can we?
In the end, the real concern here is over decreased nutritional elements, but that goes for things like boiling veggies instead of steaming them, also.
That all said, we admit that our microwaving has become much less frequent over the years. We boil water in it occasionally for a recipe when our stove-top is crowded, but eat leftovers cold more often.
Our microwave also doubles as a toaster oven, which is a neat feature, and we'll probably start using that more often.