Compared with wave out method, kernel streaming requires less CPU.
It also bypasses KMixer and Windows volume control.
It has a lower latency.
Drivers like ASIO4ALL use this to bypass Kmixer in XP.
Kernel Streaming is known to work on certain Windows Vista and Windows 7 configurations, but not with devices having WaveRT drivers such as High Definition Audio Devices integrated with newer motherboards
http://www.hydrogenaudio.org/forums/index.php?showtopic=78885