Cool idea, although it might turn into a Catch-22: once people know what the best times to submit are, those will no longer be the best times to submit. =)

You should label and explain the axes and sliders. I have no idea what the numbers mean, or what the "pickup ratio" is.

Also, instead of linking "bad" below the chart, you should make it bold and link the word "submit" instead. I thought clicking on "bad" would take me to an explanation, not the HN submit page.