In my limited exposure to multichannel music, I have heard recordings in which the surrounds were used to effectively reproduce the ambience of the recording space. If the mix is done well, and the multichannel playback system is set up well (two difficult tasks), then multichannel recordings can enhance the experience that "you are there," by presenting ambience cues omnidirectionally, just as they were presented in the recording space.
On the other hand, I have also heard multichannel music recordings in which, half way through a track, a lone violin started screaming out of one of the surrounds. My head whipped around like a gunshot had gone off. This approach to multichannel music can be very unnatural, to use Niacin's word.
Like all technology, multichannel technology can be a blessing or a curse, depending on how it is used.
Bryon