Found this in the new MSDN help. Pretty nice feature this rebuild after an assembly change has driven us nuts for years.
Managed Incremental Build Support
- The compiler supports managed incremental builds
When you specify this option, the compiler will not recompile code when a referenced assembly changes. Instead it will perform an incremental build. Files are recompiled only if the changes affect the dependent code. For more information, see General Property Page (Project).
What's New in Visual C++ Codename "Orcas"
I have notice the online MSDN is much better now. Slow but I do like the article version specific note along with links to newer and older versions.