Hi. I've been using yEd for a year. And I found that one spectatular feature would change yEd to the better significantly.
Just imagine. You are editing some scheme. And you do not have enough space at the current document you're editing. So instead making a new document, you're moving to the next page and proceeding with your editing. In this case you're not loosing your context. And your projects are grouped not in folders(this way isn't quite convenient), but in documents!
I haven't seen such a feature in any existing scheme editors yet. So, you can leave your competitors off the road :)