That would be extremely frustrating. Due to certain sensory issues, when possible I often have the (English) subtitles displayed while watching a show, as I'll otherwise just miss the odd word or phrase.

If the subtitles do not exactly match the dialogue, it is very frustrating. This happened a lot with some older shows I have the DVDs of, where the subtitles are... abridged versions of what is spoken. Impossible to use really unless you are stone deaf.