Poe's "Food For Thinking?"

Verbal irony occurs when a character says one thing but means another, as when Montressor greets his friend (whose name means "fortunate") with the words "My dear Fortunato, you are luckily met." How does Poe's use of verbal irony in The Cask of Amontillado impact your evaluation of Montresor? His state of mind, and his actions? Is he evil? Is he insane? Support your opinion with evidence from the text.