One thing I noted was how a couple of characters who started off with high standards very quickly set aside their moral/religious convictions in order to achieve short term gain.  One of course is Melibea who begins the novel as a virtuous woman, but seems to easily go against standard church teachings against immorality and suicide. 

Another is Parmeno who gives good advice to Calisto, warning him about Celestina, but who is tempted by cash.  At the end of chapter 2, Parmeno says, "I suffer because I'm loyal.  Others prosper doing wrong and I'm ruined because I'm straight and true. ... I have no choice but to follow the herd that calls traitors clever and good and loyal men fools."

Presumably this represents the author's experience with religion, that the majority of Christians are hypocrites who do not follow the teachings of their religion if it interferes with personal desires.  This is further exemplified by the priests who run brothels, and Celestina's trade not only as a bawd, but also in her ability to repair maidenheads.

The lack of a truly "good" character in the novel is disheartening.  I understand that the book is a cynic's delight, but as a reader I find that I don't care about the characters, and that they deserve their fate.