When I bought mine, which was on the first day they came out, there was a lady looking at the display models who seemed distressed by the black flicker. So I spent a little time with one turning pages to see if it would bug me.
My conclusion was pretty much the same as corona's. I don't find it any more disruptive than turning pages in a pbook. Although, to be fair, there's a lot me page flips with a Kobo than a pbook.