I'd agree with a few qualifications. First, I played around with placement quite a bit, and although I prefer a narrow angle (40-50 degrees) between fronts for music, for HT I like a 90-110 degree spread. If I do this, the illusion of a phantom center (which is only good in a narrow sweet spot anyway) becomes elusive. The same goes for the rears/surrounds - a wider spread gives a nicer field of sound, but at expense to 'center rear'.

I'm not trying to say 4/5.1 systems can't sound good, or that 7.1 isn't better, but I really think, based on my listening that dimishing returns starts to really set in. One great idea was the concept of 4/5 channels in the front of the room. I think a discrete left and right center would be useful in many cases, and most folks can localize more precisely in front than behind anyway. If I had my 'druthers I'd like to see that implemented by someone.