I have no problem with creating custom post types in PHP, but this plugin saves a tons of time: no need to search Codex for help, edit my functions.php etc.
And it provides Custom Post Types as Taxonomies! This is really cool thing, imagine you have Authors and Books post types, now you can link one to another in admin interface. Without any PHP knowledge!
I have switched to this plugin even when no need of custom taxonomies, never register_post_type() again.