The question is, how much can I write "above the fold". Ideally WordPress would always break on the "read more" fold and allow me to control the content. But I've found in many cases in the past if there's too much "above the fold" WordPress will truncate as it sees fit, which is frustrating.
So far it looks like it really does truncate where I tell it to. Granted it looses all formatting when only displaying an excerpt but I can live with that (and if I actually write out the HTML it keeps the formatting).
This content is below the "read more" fold.