Works great. You almost HAVE to have these if your going to record audio at the camera with a power microphone. If you are using them for some other purpose, make sure you check the voltage and current demands for that device (being used on the same line as the camera) before you use it.
These splitters provide a nice convenient method for splitting power. They also help to keep the installation looking neat and professional. They are great for situations where you use a camera and a powered microphone.