Dear Folks: It is proven fact that our minds are arranged so that we can read the glyphs and connect them into words either with serifs and sans-serif fonts. The real question arises when it comes to the "medium" and apparent size for our eyes.
It is also proven that while sans-serif fonts are easier to read, they are so whenever printed in big sizes. But when we talk about 8-16 we are forced to accept that serif fonts are unmatched.
I really love the Linux Libertine font. Although I would not know how could it be installed in my 505, that font is still the best IMHO.