I don't find the argument on this to be very convincing. The argument about life being 'unlikely' doesn't really mean much when 'unlikely' cannot be defined as a probability. If the chance of life is 1 out of 1 googol planets then yeah it's be unlikely to find life elsewhere. If it's like 1 in a trillion planets unlikely then you'd expect quite a bit of life in the universe (billions of galaxy X billions of planets). It's basically a rehash of the equation of the likelihood of life that is equal to a bunch of numbers multiplied together, except no one has a clue whether any of these numbers are remotely correct. Depending on how you tweak the numbers you can either get we must be alone or the universe is filled with intelligent life.
It is pretty safe to say though that given the size of the universe, even if intelligent life existed, it'd be pretty hard to reach other unless we come up with technology, or that the alien possesss the technology, that fundamentally changes how the laws of physics as we know it. I think Hawkins said that it's probably the case where basic life is very common, but complex life is very unlikely, but how likely and how unlikely, no one really knows.
