If your speakers are set up for multichannel, the left and right are too far apart for stereo.
Good Point...obviously the lack of center channel is a form of compromise, otherwise studios would not mix 5.1 with five identical speakers of equal height.
However, having a center channel at a different height from the main speakers is surely a compromise too, This was Rives point, I think, as our ears have a pretty clever way of sensing the direction of sound (try covering one ear and you will still find you can tell if a sound is above, below you ,to one side or behind you....amazing but you can). Since most setups (plasma/LCD/CRT/rear projection) preclude the option to match center channel height to the other speakers (unless you want the odd impression of the sound to come from below or above the image)...surely phantom center is a pretty solid sensible recommendation in many cases?
I agree, however, that if you can place a center channel speaker, at the correct matching height, behind an acoustically transparent screen (for example) then you certainly have a much better setup than one without a center channel and using phantom - this is without doubt. (But how many people have this option available compared to those with plasma/LCD/CRT/Rear Projection?)
