Art/Joel you said you sent a few rounds. Were all drops the same size piece or did you vary the shape?
Most of mine were the big piece, seemed like a better value at .55 than the small piece at .35.
One other thing that supposedly improves response is that if you use Pirahna's printing partner to send these out your not technically using EDDM. They use bulk mailing that is actually addressed to the recepient and references the family's last name in the headline.
Bad thing is with it being bulk mail you have like a 3 week (or longer) delivery window, so it's harder to get timing right.
Again, to be clear, I did deal with some drawbacks in doing this, to the point where I'm not doing it anymore, but it can work well.