One thing to be aware of not checking in and using mPass at the gate is that you could be bumped if you haven't checked in or visited Koru and the flight is full. Ironically this situation would be more likely to happen to frequent flyers as they're typicvally the ones who would use mPass at the gate. I've heard of it happening to a couple of friends now.
A prior flight had been cancelled in both cases and 30 mins out they then filled the non checked in seats with passengers from the cancelled flights. In both cases the only warning was getting to the gate with mPass and finding the seat had been cancelled.