In my experience, very little sound comes from the rear surrounds... even less from front high/wide. By far most surround sound comes from the sides. I get the occasional door knock or floor creak that is easily distinguished as coming from the rears, but mostly it is just low background noise. Most movies, even BluRay are 5.1, but the ones that are 7.1 add the rears, not the front high/wides. Bottom line, most of what you hear from the rears or front high/wides will be artificially produced by your receiver, and will not be enough in either case to make you say, "Wow!!!".
So how else might you use the additional speakers? In my case, it is when we have people over and I want to fill the room with soft music while avoiding a loud area near the front speakers. Then I use the multi-channel, (instead of stereo). Placement of the rears means I get pretty good whole-room coverage of "stereo" music. If I placed front highs or wides instead of rears, the multi-channel music would have 4 speakers in the front of the room, (main L/R and front high or wide), 2 speakers in the middle of the room, (surround L/R), and nothing in the back.
Some people say they like the front high/wides, and they really "open up" the sound. Others say not so much. If you only have 7.1 or 7.2, I suggest setting up with surround rears. Later if you go to 9.1, you can add the high/wide.
Just my 0.02
