This is an awesome one-shot for those looking for a solid night of modern horror. My group is new to Call of Cthulhu, so I can't say if it's "the best Call of Cthulhu scenario ever, but I can say that it was one of the best one-shots I've ever run, that I loved prepping for it, and that my players had an excellent time. If your group is particularly heavy on dialogue and roleplaying, this might take you two nights (we ran it in three hours, but I had to cut some content, and everyone felt like it would have been better stretched to a two sessions (say, six hours) - take this with a grain of salt. My group is talky as a Tarantino flick).
The pregens are great, though you may have to doctor them a bit to ensure that all of the necessary skills are present with your group (I had to get my author to amp up his occult skill to make sure the players weren't totally in the dark about what was going on). But this is a minor quibble, as it's easy to fix.
I recommend that new Keepers take the time to listen to the author's (Megan Tolentino) podcast of her session running "When the Light Goes Out" to help you familiarize yourself with directions the game could go. I took that time, and it proved invaluable in terms of my retention of narrative points.
If you're looking for a cool old school soundtrack, I advise using some tracks from John Carpenter's The Fog and Prince of Darkness to set the mood.
In short, this is an excellent scenario, and I'd love to see more modern horror from Megan Tolentino!