Just finished 5 Days. Won't say it's particularly scary, and the plot, when you look at it at the end goes fairly average from the average novel/horror movie perspective. But the presentation and handling of the story was spectacular! The puzzles are easy enough to get, not entirely far-fetched and clues aren't ample, but sort of rewarding.
Overall, I've found 5 Days a charming game, that looks completely like it came from some big shot gaming company in the early 90s.
Have started 7 Days now, and I like what I see.