True. And if you're in "multi-edit" (i.e., you're editing many card at once in a formatted card), then you're hosed (though we've ticketed fix autosave in multi-edit). But if you're editing a single card, you're in luck! We do have a working auto save feature. Let me know if that explanation is not sufficient. (Furthermore, we do plan to warn in leaving edit mode if unsaved changes).
True, we have no preview option. It has some complexities (e.g. the afore-mentioned multi-edit), but i think it's a good idea, so, add a preview option.