Hum.... downsides - yes.
How about the pollution factor in it's construction.
How about the materials used.
How about disposal of it when it's usefulness is over.
How about this modern, electric product hardly seems permaculture like
How about a wool blanket if your cold - (sorry, I just had to say it).
Okay, so I just can't take this post serious..... all stop teasing now and move on.