I think it really has to do with the source material. Some music sounds great up mixed to surround. If you can adjust the center fill on your pre/amp or receiver in Dolby Music setting you can really get some good results. One of my favorite albums to listen to in this mode is Radiohead's Kid A.
Who Uses Rear Surround Speakers For Music Playback?
I feel a very slight surround fill improves music playback. Similar to a subwoofer I set it low enough that you can't point to the sound source. I've found the smallest/affordable speakers in the rear are able to make a noticeable difference. What is your opinion on this subject?