This was a very thoughful article. I agree it is very unlikely (at least up till now) to find another habitable planet like ours. I watched an interesting documentary that stated that another reason earth is habitable due to Jupiter, whose powerful gravitational forces keeps large astroids and comets from reaching earth. And the possibility of having another planet like ours would likely need a planet like Jupiter to protect it.
And inspite of movies/scifi on visions of earthlings colonizing other planets and galaxies, with the current scope of our environment, I highly doubt that it would occur unless we change our current ways ...