I have seen it. However, I will stick with Postgrey for the time being.
I recommended in a REQUEST that Till research including SqlGrey and its interface in a future release. At that point, it wouldn't be necessary to use Postgrey.
But, Postgrey is extremely simple (see above instructions) so it isn't worth the extra hassle in my opinion for roughly the same functionality.
I'm researching an addon to Postgrey that will make it even better.
Give Postgrey a chance, use that script above to see how well it works (you will be shocked after the first full day), and see what happens.
The only false positive I have heard of was Paypal. But, that's unconfirmed and worked without a hitch for me.
You can add whitelists for domains, ips, specific emails, clients, etc... with easy in the event there were problems. Whitelists also will skip the delay in delivery.
Let me know what you all do. Please respond with your choice, if you use it, and how well it worked. If there's much of a use, I will keep building upon the instructions and make it even better (hopefully).
ISPC3 on Debian! It's great!