What's interesting about the ending of A Portrait of the Artist as a Young Man?

The ending of James Joyce's A Portrait of the Artist as a Young Man is fairly complex, and it takes a bit of time to sift through its many layers. But, on the surface, the essential meaning that Joyce means to get across is that Stephen Dedalus is preparing to leave Ireland in order to pursue his dream of becoming a great writer and artist. 

The final part of the novel continues to experiment with form, as the prose takes the form of diary entries, rather than continuous narrative. Thus, the final sections in the novel are actually examples of Stephen's own writing, rather than Joyce's presentation of Stephen's character. This development signals Stephen's increasing preoccupation with his own writing (and, if we're being honest, his increasing obsession with himself). Additionally, throughout the entries we come to understand that Stephen is leaving Ireland, and all of his friends and family, behind in order to pursue his artistic dream. Indeed, one of the novel's most famous lines occurs in this section, as Stephen vows to "to forge in the smithy of my soul the uncreated conscience of my race." Those are some pretty dramatic words, and they illustrate both the intensity of Stephen's ambitions and his inflated perception of himself.

There are two ways to interpret this ending. One way is to assume that Stephen succeeds, that he becomes a great artist and leaves behind Ireland and all of its problems for good. This version is most possible if we take Portrait as a self-contained novel. However, the second interpretation takes into account the continuation of Stephen's story in Ulysses, and so it is probably the more likely interpretation. In the second interpretation, we assume that Stephen is, in fact, a pretentious and overly confident upstart doomed to fail, and his fate at the beginning of Ulysses supports this idea. At the beginning of Ulysses, Stephen has returned home to Dublin after having dropped out of art school. He holds a job at a local school that doesn't pay him enough, he's deeply in debt, and he's exhibiting the first signs of someone in danger of becoming an alcoholic. With this fate in mind, it's impossible to take the ending of Portrait seriously.

One more final point supports the second, more pessimistic interpretation of Stephen's fate: his last name, Dedalus, alludes to to mythological Greek inventor who fashioned wings of wax for his son, Icarus. Ultimately, Icarus' blind ambition caused him to fly to close to the Sun, whereupon his wings melted and he plunged into the sea to his death. With this allusion in mind, it becomes difficult to view Stephen's ambition with any sense of optimism.