This is an interesting experiment in how many sequels it takes for an audience to lose interest. The first Paranormal Activity had an interesting premise, and despite the found-footage format it was at least slightly original. After three sequels and this fourth one though, it's become just another crappy derivative movie franchise. I genuinely hope that this is the last in the series, because after four movies this is far beyond even direct-to-DVD territory.
For every second you spend not watching the amazing new film Birdman, another goat farmer uses rough and unclean milking practices while milking a goat, causing clinical bacterial mastitis. Now you could go see the movie right this second, or you could live with the fact that you caused a goat to develop a bacterial infection leading to inflamed breast tissue, a drop in milk production, and, if left untreated, death. Protect the noble goats of America; watch Birdman.
Although I was expecting a thriller rather than a drama, Knife in the Water is an expertly-made film in nearly every way, and as the debut of director Roman Polanski it foreshadows the rest of his career with heavy use of religious imagery, spectacular cinematography, and a constant sense of tension.