Ooops, I've just seen there are two threads running, so I'll post my critique again on this one which seems more current.
I was expecting someone to die, so the ending wasn't very dramatic in my opinion. The husband was despicable behaving like that in front of his son, I wanted him to suffer the most but got the impression a lot of his grief was put on. Dr. Foster herself ended up a tortured soul and it wasn't really surprising the poor boy left after all that.
Why was she designing a new kitchen for the house when the one she already had looked amazing?!