Nick introduces himself as a person who refrains from judgement, yet he engages in nearly constant judgement in his narrative. This makes Nick somewhat dishonest, despite his other claim that he is one of the most honest people he knows.
Nick is consistent in his observations, but these observations are, largely, judgements. Nick conveys his impressions of Tom, Daisy, Gatsby and Jordan all with a sense of moral value. Even his praise for Gatsby in the end when he says that Gatsby was worth the "whole rotten bunch" of them put together, Nick is engaging in judgements that prove his self-presentation to be false.
Does this make Nick a hypocrite? Maybe it does. A more empathetic reading allows us to see Nick as a dynamic character who grows through the novel into a maturity that allows him to see himself more clearly than he was capable of early in the story. Nick thinks he is a person who he is not, an association that significantly links him to Jay Gatsby.
Fitzgerald's Nick Carraway believes he is the only honest person in the text of The Great Gatsby. Nick's father taught him early in life to avoid criticizing others because they may not have had the advantages that Nick did. Nick believes he has taken this advice to heart, but his actions throughout the novel indicate otherwise. Nick passes judgement on nearly every character except, perhaps Gatsby himself. Tom is arrogant; Daisy, superficial; Jordan, dishonest; and Myrtle, pretentious. During the party of chapter three, Nick criticized party attendees as having the behavior of people at an amusement park. He assumed that the younger men were attempting to sell insurance or bonds to the older men who had "easy money." He was so appalled by the behavior of others that he determined to get drunk, just to avoid the embarassment of it all. Somehow those actions don't correspond to someone who "reserves judgement" as Nick claims to do in the opening paragraphs.