Check for the freebie during the morning, not at night time when they are about to switch the app. I find they usually do the switch any time between 9pm - 1am EST. It likely takes time for the price update to propagate so some people might not see it free until say 2am EST. On the other hand, they start doing the change at night so if you check it too late, say at 9pm, they might have already taken that app down and started putting the new app up.
Either way I've had no issues whatsoever with downloading the apps for free.