If you want to try the Sony fonts here is where to locate them on your computer

[Sunspark]

These 3 truetype fonts are from Bitstream. They are clones of Courier, Times and Helvetica.

I'm not sure why Sony picked them, maybe the licensing was cheaper, or maybe Dutch Roman 801 looked a tiny bit better on an e-ink screen. I don't know. I can see slight subtle differences, but I can't say for sure it is "better" as the differences are very subtle so I am interested in comments from someone who enjoys fonts.

To get at them, install the Sony Reader application. Either Windows or Mac.

In Windows:
C:\Program Files\Sony\Reader\Data\fonts

In Mac:
Right click reader library.app in Applications, select explore package contents. Then path is Resources\Fonts

Edit: I was playing with them some more. I think the BitStream fonts were better hinted. I also managed to find elsewhere the semi-bold of Dutch801 and medium of Swiss721. Medium weights (thicker strokes, is in-between roman and bold) are best for e-ink I ink.