Thanks for this! Just did a cohort of 15K and it worked fine. I unintentionally hit the "back" button, but after clicking "forward" and my cohort was validated, not even 10 seconds later.

Also, I can't seem to find the place that listed which users were not valid. Did we lose that ability?

OK Edward, I added a little link to see the invalid users for your validated cohort. You just click on the "X are invalid" text on your cohort's tab. This will list the value it tried to validate and the reason it thought it was invalid.

Dan