Pride and Prejudice upholds reasonably conservative views on class. Darcy's character arc is to become the ultimate gentleman – he starts out wealthy, aristocratic, and good-hearted, and learns to add good manners and sociability to the mix. Conversely, although Wickham seems to have the outer polish of an aristocrat, he is proven to be thoroughly ungentlemanly. (And believe it or not, that's one of the more serious insults characters lob at each other in the novel.) It is the same with the female characters, whose behavior and decorum immediately marks them as either upper or lower class. Although both Jane and Elizabeth cross class lines to get married, the general idea is that they are almost aristocratic already.
Although class may determine one's social situation in life, it ultimately does not determine the respectability of one's behavior.
The novel supports the idea of class as an arbitrary – and ultimately less meaningful – distinction between people.