With or without the expansion, the hanging punctuation is a nice touch, a product of the same thesis work that gave pdfTeX its font expansion capability.
For TeXnicians: I believe that the 'margin kerning' (hanging punctuation) and the font expansion will work even if you have pdfTeX outputting DVI instead of PDF, so there are good reasons to use pdfTeX instead of ordinary TeX sometimes, even if you don't want or need PDF.