Nick, I don't have MCACC and wasn't following this closely. As you commented, you might be "way off" in how Audyssey works. What it doesn't do is to simply average different results from around the room at the expense of getting the best result in the central listening area. I requested and received references to technical papers from Dr. Kyriakakis which go into detail on the complex process involved, which was helpful in my decision to use Audyssey. The multiple measurement points(the more the better)aren't scattered about the room at various locations, but are tightly clustered about the central listening positions(suggested to be within about 2')to give as many samples as possible for the mathematical algorithm to work with. For example, see this illustration
showing that even with 12 measurement points being used, they're all at the main listening location, not at widely separate alternate locations. Also, some of the FAQs here
relate to the multiple measurement point question in a somewhat simplified way and are worth reading.
Although I use Audyssey, certainly MCACC when applied correctly has benefits and should be used to improve the overall listening results.