I find the history of Potter's Lake, the locales and the folk tales section really good and useful for setting inspirations, and the dramatis personae are not bad either. However, the two scenarios included in Paradise Lost are jokes; the shorter one is about the PC:s getting lost in the corridors of a building... until a police woman lets them out. That's it; nothing happens! The longer one, Heart of Darkness, railroads the PC:s to break into a locked dorm at the uni. They will then experience a dystopian vision of the world, and that's it! Back to normal and, yeah, maybe the PC:s will have to dodge campus security, but except for the brief quasi-religious vision nothing really happens!
Finally we have the chapter of "the secret history". This ties in with the setting of the Core rules, and I guess your opinion of the one hinges on your opinion of the other. So how do you feel about a campaign backdrop of Jesus, God and Satan having their own conspiracies and plan to fight it out? If you accept the Outer Gods and insignificant mortals concept of Lovecraftian fiction, maybe you don't have a problem with this Christian'ish war in heaven either? Well, from my point of view, that whole "Heaven & Earth RPG" angle, the subsequent "secret history" of Paradise Lost and the background story of Heart of Darkness appears restrictive and boring. The PC:s shouldn't be pawns in some grand design where their moral sacrifices decides the end of the world, but simply masters of their own fates who investigates the Paranormal and defeat some monsters along the way. As it's just $ 5, I would still certainly recommend Paradise Lost to all fans of horror rpg, but for most of us that means transferring the great Potter's Lake setting to a more grounded horror RPG (say, Chill, Cryptworld, East Texas University, In Dark Alleys, Fear Itself, OGL Horror or Savage World's Horror Companion) and ditching the lithurgical wrapping.
To sum it up, I think Potter's Lake is a nice, campy small town setting for a contemporary investigative horror RPG (like an "Eerie, Indiana" or a "Twin Peaks"). The background part and the locales for this setting would almost deserve 5 stars. On the other hand, the convoluted, metaphysical arch plot involving "the Lamb" and the two crppy adventures warrants nothing above 1 star. Which leaves me with a 3 star rating.