The Kinect for Windows 1.6 release includes changes that prevent compiling the Kinect service without errors.
The Kinect for Windows 1.6 Runtime is 100% compatible with RDS4. This is only needed if you wish to compile your own version of the service.
If you install Kinect for Windows 1.6 and you want to compile your own (User) version of the service they replace the Kinect.cs file in your samples/sensors/Kinect/Kinect folder with this one.
Remember that if you do build the service, you are building the "User" version of the service (has "(User)" in the name) and any manifests will also need to use the User version of this service and any service that partners with it will also need to be the User version. User versions of the sample manifests are provided in the samples/config directory (ones with .user. in the name).