Dialect

I think Hurston's portrayal of the characters using their local dialect serves two purposes:

The first helps the reader gain a greater knowledge as to the background, character, environment, and even circumstance of Delia and Sykes. It gives the story a much more authentic feel, which done right, is beneficial for the reader and helps one sympathize with the protagonist.

The second (and downside), is that it can give the story too authentic of a feel. By overly expanding and focusing on the dialect, Hurston is putting the reader in a position where it is possible to make assumptions and judgments that are not relevant to the story, but have the capacity to overshadow the story. I'm not saying the dialogue ruined the story for me, but I can see how it could for others.

For example, when Sykes says, "Gimme some kivah heah, an' git yo' damn foots over on yo' own side! Ah oughter mash you in yo' mouf fuh drawing dat skillet on me."

Very authentic, and it makes it clear that Sykes is kind of a dick. But I had to read it twice to really get a grasp on it. That can be a little annoying.