In my opinion, a slower pixel response time forms a more stable image because it easier for our brains to process. a 60hz monitor with a 1ms pixel response time can sharply change colour every 16ms (60hz). Now consider a 7ms response time monitor at 60hz. After 7ms of response time, it has only 9ms displaying the frame. There is a more constant, and gradual change in the slower monitor that might give our visual system a slightly easier time. I certainly find slower response monitors more comfortable.
However, with a sufficiently fast monitor, like these 240+Hz devices, perhaps that rapid flickering will occur so quickly it is beyond my perception entirely and I'll just see the 'average' pixel state. Though, my gut feeling is that I'll need refresh rates in the kHz before it stops being an issue.