I'll laugh with you guys as I figure "perfect" accuracy is +/- half stop when you consider the potential for all the other compounded errors or subjective judgement calls when metering. Meter accuracy, meter color response, what to meter, meter flare, and on to lens flare, processing differences and on and on.......

I was just out with a friend and we were getting almost two stop differences in metering off of the same silver weathered wood at an old mine. We were both metering off of what looked like middle gray but the portion he chose had a bunch of thin dark weathered cracks and mine didn't. They looked the same to our eyes but not to the meter.