In September 2009 I started to use greylisting after the spam rate on my main email address had reached an unbelievable 1200 messages per day. Here's the article that describes the event, the reasons why I avoided greylisting for a long time, and why I finally had to give up my resistance.
It is now 15 months later, and I just added an entry to my spam statistics page which makes me a very happy email user! The spam deluge has been reduced to a trickle of merely 36 messages per day, of which almost 95% are correctly recognized as spam by SpamAssassin. If ever there was a success story, greylisting at herzbube.ch is it!
After the break there is a little timeline that might be interesting to read. It is essentially a summary from the statistics page linked above.