When top executives polish their speeches, they often make a major mistake--they ask the same people who helped write their speech to listen while they rehearse it. The problem is that their assistants start to develop blind spots because they're too familiar with the subject. My experience as a radio talk show host tells me that your eyes process information differently than your ears do. Words have a much different impact in print than they do on stage.
To create the best speech, you need both kinds of feedback. My wife, the former editor and English teacher, goes over every page of my speech or workbook so that it makes structural sense...but I find it useful to sit down with some business buddies over a couple of sodas and actually deliver my speech! They're the perfect audience because I'm comfortable with them, and they can give me an honest critique.
Before you give your next presentation, make sure the people reading the speech aren't the same ones watching you rehearse.