I also disagree. My dd is a 93 Nissan 240sx, which I autocross in the SCCA occasionally. The engine is completely stock except for Iridium plugs & Magnecor wires. The factory recommendation is for regular unleaded gas, but "premium unleaded is recommended for maximum performance". I've used a friends G-tech to do some experimentation with different octane fuels, and found that with typical 87 octane fuel the car will do 0-60 in 7.4 seconds. When I filled with 91 octane premium, that time was reduced to 7.2 seconds. When I used 101 octane race gas, the 0-60 time was 7.1 seconds. These times are averages of multiple runs, all done with approximately 1/4 tank of gas. The engine management system is apparently capable of adjusting the ignition timing to compensate for the added or reduced octane of the fuel, but only to a certain point. I thought that I'd get more of an improvement with the race gas than I actually did.
Anyway, the point is that added octane can make a performance difference in some engines.