True but all of our planet has an atmosphere conducive to supporting life.
Don't get me wrong, I'm not saying that Earth-like planets generally won't support life. I have no idea how many will. It just seems unlikely that the first one found happens to tick all the relevant boxes.
Having said that, the fact that they've found one so quickly, relatively speaking, seems like a good indicator that there are an awful lot of good candidates for life-supporting planets. The more there are, one would assume, the more chance that some will have everything in place.
But then again, we could just get lucky and hit it first time. Which would be stellar (sorry).
There is good evidence that life apeared on earth more or less as soon as it cooled down, so there is just as much reason to think that this new place may have life as not.
However, by the same reasoning it seems to me that the life may be bacteria like!
The little boy in me so wants me to be wrong.