I tried an experiment this morning with my story "How to hack the media". I thought it was likely a winner on Hacker News and I submitted it about an hour before the time I've predicted is ideal for story submission (around 1300 in the UK which is 0700 on the US East Coast).
The story did not reach the front page. Of course, this is only one data point, but I'm pretty sure that there's an ideal moment for submission. Has anyone done any research into this?