Another thing worth considering is that even if the chance of life emerging appears to be vanishingly small, you still have to work out the probability of life NOT emerging. It's not necessarily as simple as one minus your first answer, because there may be other possibilities, e.g. life of a different type from our own emerging and so on.
It's related loosely, I think, to the chain of thought "the chances of the death of so-and-so being an accident are tiny, so it can't have been an accident, so it was murder" - you have to subject the alternative to equal scrutiny. In the past this fallacy has had horrible consequences of false convictions.
Returning to the case of life emerging - since we know little about the origins of life still it's wrong to assume that the chances of life emerging are so tiny. Maybe life is not that unlikely after all, since in general we see that wherever life might conceivably emerge, it does - and sometimes too we find life in places that were not thought even remotely habitable. My gut feeling is that the chances of life emerging are far higher than Hoyle thought - but it's just a feeling so who knows?