It's intrinsically difficult to argue about the probability of life on a sample of one, and so I can't adjudicated between the Rare Earth hypothesis and the Common Life hypothesis any more than the next guy. But I do think I can say that the sneering dismissal of the Rare Earth hypothesis I've sometimes seen is unsound. The Copernican Principle that "we are not special" may have carried us a ways, but it is ultimately only a heuristic, not a scientific law, and it may have limits.
The Rare Earth hypothesis as explained in the book only mentions conditions required for past events leading up to the ascent of humans to occur, and of course this paper adds to the rarity required, but the hypothesis could also extend to conditions required for humans to colonize the galaxy. There's enough rocks out there with gravity large enough for humans to build sealed-city civilizations on, scattered at greater and greater distances away from earth so as to provide incrementally increasing challenges to get to them: the Moon, Mercury, Mars, the 4 Galilean moons of Jupiter, Saturn's Titan, and Neptune's Triton. Then there's the closest, Venus, which is uninhabitable even for sealed cities but provides the challenge of terraforming. When humans can successfully terraform Venus, they're ready for a one-way trip to the stars. And the paper suggests it will be outwards down the Orion spur.
Just to be clear, I speak more broadly of the idea in general that conditions are perhaps not right for life everywhere, rather than the specific claims of a particular book.
In particular because it both easy and tempting for some people to overspecify the conditions for life and for others to underspecify. On the one hand it is trivially easy to get odds as long as you want by overspecifying exact details of human ascent. On the other hand, looking up into the sky it's hard not to notice that if life were really so easy and abundant it really shouldn't look like that up there. (Or Great Filter handwave handwave. But anyhow, something is up, and the general idea of Rare Earth is still in the running.)
