- URLs. There is mosSEF available which can be turned on from the admin page which improves urls (gets rid of query strings). There are also third party extensions which go further - keywords in urls.
- I don''t think use of the of content_item/category/module title in the title tags happens by default. I think I had to addon something here.
- Use of appropriate mark-up such as h1 tags for page/article title. I hacked the source code to achieve this - but there is a usability patch available by a8ejoomla.com
- Creation of duplicate URLs to the same content. When you create a menu item, the menu item has an ID which can be a different ID than the ID of the content item, so the same content item can end up having several different URLs pointing to the same content_item (page)
That is all I can remember off the top of my head.