Yes, I have - and indeed that would solve a major usability issue - however I live in a ATT/Tmobile dead-zone and the Twilio SIMs are issued by T-Mobile ...
So I have some weirdness in my workflow just to connect to VZW.
Oh, btw - if you use a verizon MVNO, use US Mobile and not straighttalk because straighttalk does not allow tethering whereas US Mobile does ...
EDIT: one more thing ... using a voip dialer instead of the native iOS dialer is a bit clunky but it also gives me the ability to dial from any of my twilio numbers. So I can pick my "from" number - either personal or rsync.net or (throwaway personal that we give to salespeople). So there is a pro/con involved in using a twilio SIM and the native dialer vs. using a voip dialer...
So I have some weirdness in my workflow just to connect to VZW.
Oh, btw - if you use a verizon MVNO, use US Mobile and not straighttalk because straighttalk does not allow tethering whereas US Mobile does ...
EDIT: one more thing ... using a voip dialer instead of the native iOS dialer is a bit clunky but it also gives me the ability to dial from any of my twilio numbers. So I can pick my "from" number - either personal or rsync.net or (throwaway personal that we give to salespeople). So there is a pro/con involved in using a twilio SIM and the native dialer vs. using a voip dialer...