I bought a Pioneer SC-61 and I absoulutely love everything about it, especially MCACC.
As you can see, my right speaker is sort of in a corner and my left speaker has a huge open space into the dining room.
I find after calibration it's not as boomy, but other than that not much changes. This to me means my speaker placement is about as ideal as I can get it in my current room. The only other slight difference I notice is that the center image seems to lower down to the center of my tv. Without calibration it sounds about 1 to 2 feet higher.
This is all pretty new to me, but I'm loving what all the new technology can offer.
I still run into "purists" on a weekly basis.. One is a good friend and believes the motto "they don't make em like they used to". His 30 year old sound dynamic concert monitors crush my m80s apparently
I say take advantage of the great technology at our hands.