Some parts of the film were great, other parts not so great, and the acting was bland for the most part. Keanu Reeves is the most bland and boring of all. James Spader does a decent job, with what he has to work with. The dialogue and delivery is often stiff and unnatural.
I had a good laugh in the beginning watching Keanu Reeves' character doing some lame dance along to a dance version of Rob Zombie's Dragula. That was hysterical. They brought Zombie back later with "How to Make a Monster" and I guess that was an attempt to help emphasize some horrific, monster-like quality of Reeves' character which didn't really exist. His portrayal of a serial killer was pretty comical. I didn't buy it. Maybe it would have helped if there had been more character development or back story.
As for the production, it's pretty good. The camera work is good, action is good, excellent car chase scene, and some great effects. And the soundrack was good. The music and scoring worked well with the film and was practically invisible throughout, which is the way it should be.
In all The Watcher wasn't a super bad film, just could have been improved upon. I don't know if I'll watch it again. Maybe I will give it a second chance.