In our Visual Studio documentation we stated to get round-trip engineering documentation you needed Visio for Enterprise Architects. This is not the case in Visual Studio 2008 as this feature comes will versions of the Visual Studio 2008 Product family. unfortunately it looks like this has caused some confusion in the forums and we are correcting this documentation asap.
I have included David Trowbridge's reply as he also indicates additional functionality will be forth coming in the future.
Short answer: Reverse engineering of code in to Visio UML models works with the combination of Visio Pro 2007 and Visual Studio Team System for Software Architects 2005. It does not work with Visio Pro 2007 and Visual Studio Team System Architecture Edition 2008. However, Visio Pro 2007 does allow you to do reverse engineering of databases.
Why?: The ability to reverse engineer code is now provided by all versions of Visual Studio in the form of the class designer where the code is continuously synchronized with model. Additional modeling functionality will be provided within Visual Studio Team System in the future.