Surprised nobody's mentioned the Discovery separating the saucer section. From what we saw, it looked like a mechanical separation, rather than the programmable matter separation that the nacelles use. I don't think there are any impulse engines on the saucer, but I don't think that's a problem for a ship that's been retrofitted with 32nd century technology, since I don't remember seeing any visible impulse engines on any of the 32nd century ships. EDIT: Impulse engines are visible on some ships, but not all.
Speaking of 32nd century ships, I'm a little disappointed we never got to see a proper 32nd century bridge. I don't count the Discovery's, and I'm not sure we actually saw what could be called the command bridge of the USS Federation.