I couldn't find a recent thread dedicated to the Yokohama so I thought I would throw this in here. I am on my third year with the GO15s, about 40,000 miles now, and the tires are down to the first wear bar.
The snow performance has gone down significantly this winter, compared to the last two winters on them. Especially in the greasy slush that happens on chemically treated roads with only a couple inches of snow. The first two winters I thought they were nearly as good as dedicated snows. This winter, they slide a lot more, and the rear end feels really loose at times, even on a neutral throttle. They are also getting noisy on certain types of road surfaces. Smooth blacktop is the worst.
I will use them the rest of this winter, but they will definitely be getting replaced by fall of this year.