Here's a funny thing, when Fortunato keeps scoffing that Lechresi "cannot tell Amontillado from Sherry," well, that's actually somewhat ironic. You see, apparently Amontillado is actually a type of Sherry. It's darker and only had the slightest difference in structure and taste from other types of Sherry. In fact, some wineries only categorize Amontillados by a their difference in color. For your comparison, here's a basic glass of Sherry:
And here is a glass of Amontillado:
Only slightly darker. But, what bearing does that have on the story? Well, bear in mind it was intoxication that allowed for Fortunato to be lured to the chambers of his demise. His knowledge, his expertise in the field, his arrogance and chastising of others as such played into said doom. This could be a commentary on the futility of the "overcultured," those who have too much time to waste on frivolous things that breed arrogance about the pointless. I believe in some way, Poe (who had exposure to that kind of lifestyle) was trying to show that kind of lifestyle and mentality only leads to horrible and ironic doom. It just shows that a little knowledge (and too much wine) can sometimes be a dangerous thing.

