I think the greatest strength of this novel lies not in its characters, but in its structure. It is made up of scenes within scenes within scenes and each serves to illustrate a larger question about the relative merits of introspection and worldliness. For example, the scene where group of the characters play a game called "speculation" the individual qualities of each person are illustrated in their behavior in the game which can be viewed as a microcosm of the whole novel. Similarly, the various marriages that are depicted (and the households centered on those marriages) are a study in contrasts. The episode of the theatricals that are put on early in the novel are also a smaller scale version of the story that plays out throughout the book.
In his introduction to this edition (which includes a ton of spoilers and should not be read under any circumstances until you have read the novel) Tony Tanner says "the novel thus reveals a battle between worlds as well as concentrating on the relationships of a few characters." He is referring to a conflict between the old agrarian world and the new urban one, but I think the observation applies equally to the battle between a life of quiet contemplation (Fanny, Edmund, and Sir Thomas) and one of worldly activity (the Crawfords and Mary Thomas).
Fanny Price is a heroine unique in Austen's novels in that she is without faults. Edmund is more typical of the center of an Austen novel as he is a good and virtuous character who has flaws (really one big one in his case) that he must struggle with and his success or failure in overcoming it determines his ultimate fate.
Overall I thought this was an excellent novel full of complex, thought-provoking questions of morality that were, as it typical of Austen, thoroughly woven into a compellng story of romance and family life.
Other thoughts on this novel:
Brona's Books
Anneish Imaginary Adventures
Sense and Sensibility by Jane Austen
