Yes, I'm having the same problem. I think perhaps it's because of the contrast. The bold black on white is perhaps a bit too contrasty? Maybe make the background slightly off-white (like HN does)?
Otherwise, looks awesome! I'll add it to my bookmarks :)
I don't know why, but it makes my eyes tired to look at it, as if I was looking at red text on green. Other than that it's great.