While I feel you pain there is something that you ought to know about the SGC process workflow. The 20 day "turnaround" is not indicitive of the day on which the cards will ship but instead the day on which the cards should be graded. It is then generally 2 to 4 business days prior to the cards shipping. If you add the 5 day lag that was caused by the national convention, things aren't quite so bad as they seem.
Based upon my experience using the "sister" company CGC for grading comic books, SGC is light years ahead relative to promised delivery time.
Again, I share your pain as I've had shipments late before but overall I am more than pleased with SGC service.