Well, actually I haven't read it yet. But I've ordered it, and at this moment I'm eagerly awaiting its arrival along with other astrobiology books.
The start of my post was based on what I knew(or what I thought I knew) about the Rare Earth hypothesis.
I do agree that life probably would have looked totally different today, if it weren't for all the incidents and mass wipeouts occuring in the distant past. Humans, or for that matter creatures with human-like intelligence would probably not have existed today if the dinosaurs didn't go extinct 65 million years ago.