Right now, if you want to create a link to another of your post, you have to get to the public section of your blog, copy the url of the post you want to link, get back to the admin interface and paste the url.
If you ever want to change the permalink structure (it's not a very good idea, but you maybe have a reason to do it), all the links inside your posts to others posts will be broken.
There should be a solution for this. There is a special tag to insert the "Read more" link, there could be a special tag to insert a link to one of our post.
I am not suggesting the syntax of the tag, but just the idea. We could have someting like <!--42:The text of my link-->. There is two parts in this special tag. The first one is the id of the post, the second one, is the text that should be use for the link. If there is no text (<!--42-->), the title of the blog post should be use for the link.
Like this, we would never get afraid to break our links. WordPress would do the hard work of creating the link to the post (using the id number in the special tag) each time the page is displayed.