I agree with Susan in that VerifyApp is limiting.
Example: Just this past week, we used Verifyapp and used the "Mood" survey. 90% of the participants came back and told us that the screen switching (the time between showing the screen and then asking for their feedback) was too fast. They were not able to pause the screen. In most cases, the participants had to click "back", which then kicked them out of the session.