Uneven. Atmospheric and scary at times (opening/the death sequence with the neighbor/car chase/ending) but its ear for dialogue and acting is often awkward. Other times, its scare scenes are silly (killer trees?) and its situations are underdeveloped and/or forced (the attempted rape at the park.) Lacking, but still with great creativity. It's a film that could've been much better... and much worse.
This is a cinematic case of taking two steps back for every step forward. While the villain has her intriguing aspects, her moronic actions spoil any aura she has. While it has its suspenseful moments, the story feels padded with dropped subplots and overlong chase sequences, and it follows the "nanny from Hell" tropes far too closely to be anything truly special. Also, for a Friedkin film, it's pretty badly edited.