I agree it would be foolish to think that there is no other life out there. Oddly enough, I bet it is more similar to life that is now, or once was on this very planet we live on. (Life is life, the same properties that make up the earth, our solar system, etc. are the same way out there, so therefore, it might be more like looking in a mirror than you think.)
As far as inteligent life visiting us, little green men and all, I'm not so sure. We have a fairly good grasp on physics, and traveling thousands of light years is not that easy (physics is physics irregardless of what planet your on). Even if you could travel the distance, you would be thousands of light years old when you got there, and when you finally made it back, who know if the earth would even still exist. We are talking about a really long time you know. When you look up into the sky at night, the light you see coming from all those stars is actually quite old. A star might explode today, a long ways away, but you wouldn't know about it for quite a long time (years).