In case you weren't aware of this, you can use the WBS Modeler tool to visually model and plan your projects or to validate the current structure of your project. The tool uses Visio 2007 and Project 2007 to do this.
Ok, I haven't used this yet. I'm in the process of installing it now. One of my fellow PMs sent me the link so I'm passing it on to you. The documentation says you can generate Project schedules from a Visio WBS diagram. This sounds very cool and I'm looking forward to trying it out. If you've used this already or are going to, comment to the post with your experience.
There's also some documentation around how to do Visio based reporting on Project data using Pivot Diagrams. More info can be found here: http://msdn2.microsoft.com/en-us/library/aa827350.aspx There were some Visio based reports shipped with the Project 2007 client. This article goes into detail as to how that was done.