Integrating Visio 2007 and Project 2007

Microsoft Office Project 2007 and Microsoft Office Visio 2007 provide integration capabilities that previous versions did not provide. You can take advantage of these capabilities by using a combination of native features and COM add-in features.

The Visio Enterprise Project Management (EPM) solution uses standard Visio diagramming features, such as groups and connectors, together with new Visio 2007 functionality, such as AutoConnect.
The Visio EPM solution also provides the following tool-specific shapes to use for
creating a process flow diagram or a Work Breakdown Structure (WBS) diagram:
Project Group. Represents the highest-level shape, which encompasses multiple projects
Project. Represents all phases, tasks, and milestones within a project
Phase. Includes all tasks and milestones, such as a summary task in Project
Task. Represents an individual work item; used when you create a process flow diagram
Milestone. Signifies the completion of a major task or project event
WBS Task. Represents an individual work item; used when you create a WBS diagram
Task Connector. Enables you to represent the critical path in process flow diagrams or to create predecessor relationships and successor relationships in WBS diagrams

Here are few examples what we can do with this:

All of these can be generated on the fly as you run the project in microsoft project. I see it as great advantage - it helps presentation of the project to your boss like breeze

For detail please visit this msdn article, you will be glade you did:
http://msdn2.microsoft.com/en-us/library/aa827350.aspx