For VB6, the Make VB6 action provides incremental build logic, building only those projects where the source code is older than the compiled executable.
For VC++ (VC6 and VC7), incremental build logic is provided by the Visual Studio (which the Make VC6 and Make VS.NET actions ultimately call to perform a build).
For C# and VB.NET, true incremental building is not currently available; see this thread for details:
http://www.kinook.com/Forum/showthread.php?threadid=303