The main advantages are :

• Easy install and uninstall without losing any data.
• Compatible with most of the com_content modules: Most of the slideshows or news modules for example are displaying the last articles from a specific category.
• Compatible with most of the com_content plugins.

The principle is quite simple: you chose an existing content section in the general configuration of FLEXIcontent. The component will then be able read all the categories and items assigned to this section.

Why only ONE section? Because it’s my decision and I’m the Boss :-) No, more seriously, it's just because categories are now nestable. You don’t need the sections anymore. You just have to recreate the categories hierarchy by using either the standard copy/move function from Joomla’s category manager or the new "import Joomla! structure" feature from FLEXIcontent beta4. The import tool will create a new section for you and copy and convert all your Joomla! structure into categories - sub-categories - contents. (more about the automatic import tool)

Then just go to the items screen and bind the contents to their extended datas.