OK, thanks for the responses.
Now I'd like to elaborate on why I like the long wall placement. First, music halls and I'm going to throw in cathedrals are long and narrow for a couple of reasons. First, it's easier for the audience to look forward rather then off to the side so this design is natural. Next, it does put most of the audience an acceptable listening position. Third, the long narrow construction of halls and cathedrals creates a large, natural reverberation which most people believe, enhances the music, giving it that "heavenly" sound.
Now if we put our speakers into that same configuration, a couple of things are going to happen. First, the distance between the speakers will be much closer then if we set up on the long wall. That means the equilateral triangle that George Cardas talks about is very small. If your speakers are 6 to 7 feet apart, then your listening position should be 6 to 7 feet from the speakers (at the intersecting radius from each).
Another problem with the short wall is exactly what happens in the concert hall or cathedral, that is many early reflections. So then people use wall treatments to reduce the natural reverberations now occurring in their living rooms. They are witnessing first, second, maybe third generation reflections and they are crossing the sound stage and destroying the stereo image as well.
Another problem with the short wall was addressed by Polk Audio with the SDA (stereo dimensional array) system in which the left and right speakers were connected by a cord to introduce out of phase material to each speaker. What this did, was to reduce or cancel what is known as cross-talk distortion. It prevented the left ear from hearing the right speaker and the right ear from hearing the left speaker. I owned a pair of these speakers and you could close your eyes and point at a speakers perceived location, and then discover you were off by 10 feet.
The long wall offers natural cures to all of these problems. Because the speakers are further apart, the equilateral triangle is much larger and there usually is enough room for several people to witness the "sweet spot". Next, early wall reflections are taken out of the picture as most first reflections are going behind the listeners. To me, it is very important that the listener be well inside of the equilateral triangle to hear maximum stereo. And the spread of the speakers reduces or makes moot of the cross-talk distortion discussed earlier.