I attempted to get my coolant flushed and oil changed today, but the shop apparently wouldn't be able to squeeze me in before they closed tonight; so I'll go tomorrow.
However, when I was out running other errands; I parked and let the car idle a bit (with ECC off)...as expected, the temp gauge creeped up, and I noticed that the fans near the radiator didn't come on until the gauge was pretty high. I'm not sure if it'* the thermostat or if it'* the sensor like willwren suggested.
And, as I was sitting in a left turn lane forever waiting for a gap in traffic, the temp stayed just under 200, which is where it had always been before. Given the info you all gave me in this thread, that made sense (since I had the ECC on at that point).
Does this help any with narrowing down the problem?