I still get spam in my inbox regularly. I'm using google postini to do the filtering, in my situation I wouldn't classify it as "quite effective".

Are there better alternatives I am not aware of?

I use the default GMail filters - perhaps I'm just lucky and receive easily filtered spam. I get hundreds of spam messages per day, and none break through on the average day.

Hundreds a day sounds plausible. So with that much crap to wade through, how long does it take to finally discover and rescue false positives from the spam folder?