My post [1] made it to #8 on the front page last week and stayed there about 5 hours. I haven't made proper analysis yet, but here are rough numbers. The page got ~3500 visits, most of which within the first 24 hours. Most concurrent users was ~80. The first 24 hours got the linked app ~500 downloads, so that would give a pretty good conversion rate. I don't have data on how much of that came through the website or HN, though.

[1] https://news.ycombinator.com/item?id=8070131