I thought Steel was a clever idea but the ending sorta just ended...no real resolution.
I really like "Steel," but, of course, I'm biased.
FYI: Tor is publishing a new collection, Steel and Other Stories, this October, just in time for the new movie version.
The collection also contains another old Matheson story, "The Splendid Source," that, bizarrely, was recently adapted into an episode of Family Guy. Really.