On my commute I have over 30 miles of nearly straight interstate highway. I have one turn as I'm nearing the office that's about 110 degrees, where I'm leaned over at 10 mpg enough to have scraped the pegs a time or two. No problems. What concerns me most is riding home in the pouring rain on tires with no channels that would send the water out to the edges. I made the ride once that way and didn't have a problem, but I held my speed to 45-50 mph all the way home. (And actually passed a few cars whose drivers obviously had no idea how capable their tires actually are!) In any case, I would like to have a more modern tread design just for days when the weatherman is wrong, or when he's right and I am too foolish to believe him.
Fortunately, the Speedmasters did fine last time out, so I'm no longer really worried about it.