In their FAQ they haven't addressed the security issues when connecting to public WiFi hotspots. The user's traffic would be flowing unencrypted, easily accessible to strangers. I wonder if they'll be providing free VPN service when connected to public WiFi.
Quoth the source:
Know your data is safe
Your data is secured through encryption when we connect you to open Wi-Fi hotspots. It's like your data has a private tunnel to drive through.