Spam passing greylisting.

Hi all,
Everytime I mention greylisting I fear I'll start another arguement,
so if you are against greylisting in concept or practice please ignore
this thread.
For those of you using it, are you finding more and more spammers
are passing through greylisting? Example:

X-Greylist: delayed 364 seconds by postgrey-1.21 at wedmore; Sun,
05 Jun 2005 17:31:21 BST
Received: from 85-250-125-41.bb.netvision.net.il
(85-250-125-41.bb.netvision.net.il [85.250.125.41]

Now this system retried about once every 2 minutes, until it got through. Are you finding this happening to you? Is there anything we can do other than increase the delay?

Dave.