No Digital surround sound
IGN have managed to grab a copy of the official Wii documentation which confirms that the console will not support digital surround sound.Although we can't rule out any last minute changes, it looks as though Wii will utilise Dolby Pro Logic II.
So, Nintendo's new system appears behind the times when it comes to certain capabilities, with no HD support and no digital sound. Nintendo obviously feel that the introduction of digital surround sound isn't required as Pro Logic II seems to have done the job well enough on the GameCube.
Whilst Nintendo are 'old fashioned' in the audio department, they certainly make up for it with the new controller and range of innovative games.
Source: IGN