I tend to agree with the first-impressions idea, but then there are those with social issues that never make a good first impression -- but they may be wonderful people once you give them a chance. So, I wouldn't want to live by that.
Besides, if we're always waiting for the perfect fit, we may never find a friend. I think it's great, Garga, that you went ahead and became friend/acquaintances with those people. Even if at the end it didn't turn out to be a life-long friendship, at least you tried.