At this time, notifications can either be enabled or disabled for certain items, and all items will either have an email sent or not based on this setting. It would be nice, though, to be given the option to either send an email notification or not for certain workflow items (e.g. to have a checkbox for whether a notification should be sent or not), and to be able to make this decision on an item by item basis at a certain point in the Workflow (e.g. after an item has been approved).
This would give greater flexibility with regards to the manner that notifications are sent.