In the interim, PDFCreator is a free win utility and does a great job of
stripping the extra bytes away: simply install, select PDFCreator as your
printer and print. The resulting output can be 80% smaller, or more.
http://sourceforge.net/projects/pdfcreator/
For Mac OS X users you already have an application that will do this. I
just open the .ps file in the "Preview" application and then do a "Save
As..." to a .pdf file. One example I have is a .ps file that is 1.2MB in
size. Lilypond generates a .pdf file that is 364KB. The file that I
create from the .ps file ends up being 84KB.
-Eric