I'd hazard the opinion --as a USAmerican-- that the lovely shwa is more common in (at least) the NE, MidAtlantic and some parts of the Southern US and that "aye" is really only used when referring to a particular object, or for especial emphasis, e.g. speaking to my mostly deaf father.

At least, reading that last sentence in the post, I can think of only 1 or 2 people in my acquaintance that would use "aye" as opposed to "uh".