Bloom doesn't like Boylan much (unsurprisingly), and Boylan's perspective is one that is noticeably absent from the novel. Realistically, Boylan is small-fry. He's a popular guy in town, something of a womanizer, and is more than happy to jump into bed with a star singer if the opportunity presents itself. Other than that, there's probably not too much that we get to know about him.
More than any one character, the antagonists in the story are largely ideological: the oppression of the British, the stifling influence of the church, the omnipresence of anti-Semitism at the turn of the century, the narrow-mindedness of Irish nationalism, the temptation for an ordinary man to fall into a cycle of self-pity and despair. Throughout the novel, we see Bloom chart his way carefully through each of these challenges of which Boylan (or any one character) is, ultimately, only a small part.