Who Uses Rear Surround Speakers For Music Playback?

For me it's a NO. But whatever sounds good to you.
Fuzztone - Be more polite and no racist comments.

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.

I use the rear speakers and center when I listen to classical multi channel music. Some that are recorded well are fabulous. Some not so much. It depends on whether the recording was actually made that way.