I have long been a microwave avoider. Microwaving food and drinks changes the molecular shapes of everything exposed to microwave radiation.
In addition to the chemical changes that occur in microwaved food – even water! – the heat of microwaving can also speed up the leaching of toxins from plastics into your food. Dr Mercola has a great article outlining all of the ill effects of microwaving. Click here to read more.
More recently, I came across this article about microwaved water killing a houseplant. You can try this little experiment at home.