I can tell you one issue I observe as someone living in a different timezone. HN ranking highly depends on timing. As a consequence during hours the US is asleep my impression (I have not investigated this thoroughly) is that front page stories are dominated by old stories and new submissions don't make enough votes to get to the front page. Then once the US wakes, New stories get enough votes and make it to the front page. This leads to biases in the news, which I find unfortunate, because I believe everyone would benefit from news being geographically (for lack of a better word) broader.

I certainly welcome someone playing with different algorithms to see how they affect ranking.