There are a few problems with that experiment, lack of "blinding" and too small a sample size, to name two. If you don't want a microwave, there are plenty of other good reasons not to get one. They take up too much space, and everything you cook in there (even water) ends up tasting like lasagna.
I love your blog!
As Anonymous before me has said, this one is another of those internet memes with far less truth in it than one might initially think.
http://www.snopes.com/science/microwave/plants.asp
Having said that, we don't have a microwave - because of the space issue rather than any fears about food.
Thanks, you two! Yes, I did realise that there were a few problems with the article, but I was not going to get a microwave to do my own test and I did not think of checking snopes, who actually did (I enjoyed reading that). But you are right, there are enough other reasons not to get a microwave oven.
Hi Kati, It should also be pointed out, for the sake of general information, that microwaves generate electromagnetic radiation similar to the type that conveys radio and television signals through the air; microwaves, however, have a different wavelength. Microwaves are not high-energy ionizing radiation, which are notorious for causing damage to organic tissue (gamma rays, etc.). The concept that microwaves damage food simply by passing through it is fundamentally false.
Hi Kati, As far as your gran and the metal plate: This is a dim memory, but I remember reading that microwave oven shielding (in terms of preventing leakage) has improved over the decades that they've been in household use. People with pacemakers used to be advised to avoid the area around a microwave oven because earlier pacemakers were apparently susceptible to interference. I don't have a source for these claims at hand. Microwaves are electromagnetic radiation of a higher frequency than TV and radio waves, but not so high as visible light.