Finally! Those watching the episodes in sequence know that so far Cap. Archer had the most annoying tendency to think himself like a God and his duty to solve all problems of the universe, without ever considering the consequences.
Oh, I know you can say this is part of his characterization, since the Prime Directive doesn't exist yet, but for those of us who have seen Star Trek before and know the importance of the Prime Directive, it can seem very obtuse and distressing.
Well, finally he learns the lesson, thanks to a great Phlox episode, which makes him quickly jump to my favourite character in the series. His example with the Neanderthals is precise: imagine that when the Homo Sapiens were driving the Neanderthals to extinction that some alien came and helped them survive. It might have saved hundreds of thousands (millions?) of lives them, but everything the human civilization would come to be would be lost.
You can ask if it is worth it or not, but the point is: it is not your decision to make. You shouldn't interfere in complex situations without knowing all the facets of the problem (and you rarely do). It is worth noting that one of the coolest things about the Prime Directive (and Star Trek in general) is that it is not something about science fiction, it is something about human (or sentient) interaction, and it makes you think about things in our world too.
Anyway, I give it a 9 mainly for Phlox teaching Archer what the Prime Directive is all about, and seeing Archer stumbling everywhere over complicated issues so far, that is quite a feat! But the rest of the episode was interesting too, I would give the rest a 7.