My listening experience does not include 5.1, but I have had a few friends who were interested in rear channels for ambience (including one who used Klipsch La Scalas in the front and Heresies in the rear). Personally, while intriguing the idea seems somewhat contrived: When you see a performance (generally) the action is before you. The ambience is created by some speaker placement beside and around you, but it is the aarchitecture of the hall that provides much of what you hear and discern (right?). By the same token, instead shouldn't folks put more stock in treating their rooms or finding a way to process signals (DSP?) than putting speakers everywhere? I use two mains and a sub, and while the set up is far from ideal, toeing in and tilting down has served my purposes rather well.

At the same time, I agree: there aren't many albums recorded in true multichannel format (I reckon). Remember when Quadrophonic was all the rage? What happened to that hallowed thing?