Interesting to note that you've hosted your beta clients on Kim Dotcom's Mega service. This is the first time I'm coming across a legit & popular service hosting its public client files on Mega.
I love PIA but I was too afraid to use it at Black Hat / DEFCON this year. If you use L2TP (required for iOS, handy for OS X because there is a native client) there is no certificate to prevent a MITM. Is there any way to address this? Can you use a certificate instead of a pre-shared key?
nitpick: There is a native OpenVPN client for iOS in the AppStore. I don't know how they managed to, but it's plugging into the native iOS VPN functionality and it works perfectly well.
To my knowledge, there are 7 companies including OpenVPN who have been granted access to private VPN APIs. I personally use the OpenVPN iOS client for "always-on" phone VPN.