Here's what I get, an 850K PDF, if I just plug the plain vanilla text of Robinsono Kruso into ConTeXt along with a few lines of configuration. Pretty good, considering that's all I did. This is with micro-typographic font expansion, where the glyphs are widened or narrowed ever so slightly, to give the line-breaking algorithm better chances. However, and I'd forgotten that this would happen, the resulting PDF is a few times the size of the PDF without the font expansion. That's a really serious drawback.
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.