In the first 2 weeks the pop was immediately up to 8 or 9 iirc. So quite a bit of cards were sent back in.
You could probably check the certs from this thread:
www.elitefourum.com/t/ninetales-no-damage-error-population-report/30682/1
The cards were probably just sent back in, so you could see if the certs are still just shadowless or if they are changed to no damage shadowless, then you can see which ones are new and which ones are sent back in.
As for a datapoint, I got an offer for $750 for my PSA 6, no money was exchanged so do with that info as you will.