I flew Continental with Pixie from Cleveland to Florida and it was a breeze. There was not even so much as a second glance toward the carrier or Pixie inside. No measuring and no twirling. I paid for her when I booked my ticket online so I don't know if that made a difference.
From what I've read, it can really depend on the stewardesses and who's working at the gate. I've had flights where Pixie has been able to sit on my lap the entire flight. You should be fine because you have a bag that is made specifically for flying. Good Luck!
