Just back from seeing it a second time and I really enjoyed it again. After a fairly disappointing summer, it is so refreshing to see an engrossing film that doesn't just throw CGI at the screen and treat us like infants.
There are certain moments in the movie that I really like, Spoiler: especially when Sarah runs to the foot of the stairs after Sid falls. Everyone thinks she is running to catch her son, but then she grabs Joe and pushes him out of the house - a real "WTF" moment because her immediate instinct was to escape quickly knowing the fury her son is about to unleash. Wonderful cinema!
I loved Jeff Daniels' line, "I'm from the future, go to China" :)
I agree that showing older Joe murdering an innocent child was a brave move, but I think his reaction afterwards of deep pain and regret at what he is forced to do is a good balance. He is not some emotionless killing machine, but someone who is overcome by intense guilt at causing the death of the women he loves.
Let's hope this doesn't make the same mistake as The Matrix and end up producing low quality sequals.