A couple of changes I've noticed in the last few days:
1. After completing a survey, instead of going to the "rate the survey' screen they've had forever, it just brings up a screen and says you've been credited (and luckily, so far I have indeed still been getting credited). The flow isn't as good, because of taking you to a new survey, you have to get back on your own to the home page and look for a colored button again, or go back to e-mail
2. And possibly related, after a short time in which the button was reliable, I'm seeing that sometimes you have live surveys on e-mails even with a greyed-out button. That fix didn't last long.

FTF