Comments will no longer be stored in a hidden forum. With the node model, articles can each hold their own comments. The commenting system is the same used for other content types to allow for portability.
Sections and Categories - These were confusing in vBulletin 4. In vBulletin 5, there will only be Categories. Each category is a channel in vBulletin 5 and can hold one or more article nodes. The main channel will be "Articles" and it will be on the same level as Forums, Blogs, Groups and Special. The Articles channel should not be deleted. Article categories are managed in the AdminCP either in under the CMS section or Channel Management.
Tags are the primary method of multi-category organization. The vBulletin 5 CMS uses the standard vBulletin Tag system. Tags are not assigned to categories but can be used across categories. They function the same as tags in forum topics and blogs. They can be searched in the same system.
Grids, Layouts and Widgets - These are replaced with Site Builder's functionality. The Site Administrator can use Site Builder to add pages, edit Article Categories and add widgets to the user's view. The Layout step has been eliminated. Grids are now Layouts. Widgets are called Modules. Page templates are previously stored page configurations.
Author and Editor Usergroups – Two new usergroups have been added to handle article creation and publishing details. Most sites have a limited author pool. These groups allow you to develop a workflow to create and publish articles on your site. With the default permissions, Authors can create and save draft of articles. They will be able to edit their own articles before publishing over multiple sessions.
Channel Navigation Module. This replaces the Section Navigation Widget in vBulletin 4.X. It can be placed on any page and allows you to choose the Top Level Channel to be used. This means you can use it for Article Categories, Forums, Blogs, and Group Categories. An example would be to place it in a Forum Category to get a quick navigation box to all of its children.