I agree with newms. It is unfortunate but even when you have a lot of really good replies from POI's it is still common for them to reject you. I had a really nice 45 minute phone conversation with one POI and I received a prompt rejection from that school. It happens. However, I'd like to think that most positive replies (more than just "I encourage you to apply", but things like "your background is exemplary", "you would be a great fit here", ect) have a positive impact on your application.