From what I have heard Dolby PLII works great at turning 5.1 to 7.1 (compared to just having a 7.1 soundtrack) since it isn't hard to just fill in the gaps with panning and such. How much of a benefit 7.1 is actually depends on the size of your room though. If you have more than one row it can probably be beneficial, if not it probably isn't so much. By that same token I can see how the front width can help with panning and making a larger front sound-stage. But, with the height channels I get the feeling that just sending the out of phase stuff here might not really do much, especially if I am going to have to spend $400 to $500 to get some QS speakers to do this small improvement.

It's really too bad that somehow 7.1 with four surround channels has become the norm over doing either height or width in the front. All the designers of this stuff say that it is much more beneficial to add more channels to the front than to the back.