Using Ellipses (. . .)

In college, I learned that ellipses are used for omissions while dashes are used for stronger-than-comma pauses, especially used for emphasis. But I see ellipses used for pauses, especially in dialogue, all the time. Is it poor grammatical usage to have ellipses as long pauses?

My college text book, The Allyn & Bacon Guide to Writing (3rd ed., eds. John D. Ramage, John C. Bean, and June Johnson; New York: Pearson, 2003), only mentions ellipses for the use of omission within quotations (cf. 625-26, 807). However, Grammar Girl describes the usefulness and acceptableness of ellipses in formal writing, appealing to the Chicago Manual of Style. Indeed, §11.45 (15th ed.; Chicago: University of Chicago, 2003) of the aforementioned manual clearly states that ellipsis points may be used in speech indicating faltering or fragmented speech due to either confusion or insecurity. It also states that interruptions or abrupt changes in thought are indicated by dashes.

As a result, fictional dialogue might use ellipses to show stuttering, faltering speech, but a formal essay would use dashes for any sort of intensional pause and ellipses for uncertain pauses. In either case, dashes or ellipses, these punctuation marks should be used sparingly, and furthermore, I would argue ellipses should not be used in formal writing as the author should be deliberate and confident in the argument presented, though I admit there might be a time, however rare, that an ellipses could serve its purpose to note an uncertain pause even in formal compositions.

What do you think? How do you use ellipses? Do you find them effective? Do you find them annoyingly overused?