Considering Rand pretty much sumarized the point of the book with "This is John Galt Speaking" chapter, I think she really could have spent less time on reiterating that collectivism is wrong and more on character development. Her ideas are powerful enough to make the book worth reading, but it could have been so much better.
Rand's method of creating her characters is different from virtually any other novelist's. Each character is designed to illustrate a philosophical principle, or to expose a philosophical error (Rand was not trying to merely create interesting characters). Two examples: Reardon was productive, but altruistic. Willers was productive, and admired the "good guys" in the book; but he acted entirely on emotion, which is why he was excluded from Galt's Gulch at the book's end. (Willers is a very subtle character, and his unfortunate end at the book's climax is usually misunderstood by readers, who missed the flaws in his character.) Even the minor characters are very carefully drawn, if you focus on their philosophical significance. When you try to understand what Rand was doing -- philosophically -- in writing Atlas, you can really appreciate the work far more than if you merely read it as "just another novel."