Awful.
The conceipt of the central plot is intriguing, as in the original, but this film is ruined by several factors.
3 of the worst irritants are the most annoying child in the universe hogging the dialogue, Bates hamming up a terribly written part and special effects making the last scenes of the film almost terminally dull dull dull.
Reeves is ideal as the emotionless expressionless alien and the scenes of his interrogation along with the first 15 mins scene setting are the only highlights.
Avoid.

It's a real shame that this film seems to be missing something. There's nothing wrong with the acting, the effects aren't that bad but the script and the story are just weak. You can infer from certain (limited) events why Klaatu makes the final decision he does but further situational developments would have helped to strengthen this ideology. All adds up to make another average day at the office for Hollywood.