Hi Steve,
Not sure what profession you are in but our (landscape) office produces some very graphically complex drawings with lots of hatches, fills and symbols. We get a few complaints from Architects offices that our .pdfs take a long time to regenerate on the screen usually because of some of the hatches we use.
As a rule we try to keep the .pdfs under 10Mb for emailing.
The best way that I have found, so far, is to use the 'Export PDF' function and then reduce the file size further using Adobe Acrobat's 'Reduce File Size' command. It seems to keep most of the intended clarity without 'greying' objects.
Creating a 'postscript file' using VW print manager and then compressing it with Distiller is the best way for producing really small file sizes but we find that it gives a very 'washed out' final product.
As previously suggested experiment with the DPI output.