i've found that black text on a white background is much easier on my eyes than the opposite, at least on the newer, brighter LED LCDs, especially the glossy ones like what ship on current macbooks.
from talking to Giles (I work with him), I think his problem with hacker news is that it's basically turning into another digg/reddit/slashdot type of thing. It's basically a pool of links outlining what's popular with whoever the users of the site are at the moment, and that group of people is likely to change over time.
I think what would work better is a pool of links that shows you stuff you might find interesting based on past usage (voting up/down, friending others, etc). Don't show me what's interesting to everybody who reads the site, show me what's interesting to _me_. As Giles has said in the past, I have a need for better filtering mechanisms.