I got the 19A availability popup yesterday and updated it.
I've been running on 18C since I bought the car back in December, 2018 and the dealer didn't update it when I took it in for the brake regen recall.
On 18C I got the blank screen problem twice. Also the infotainment system had some issues. Like forgetting my presets for the interior color lighting, logging me out of my Live account, displaying the car icon on the dash when it was supposed to be showing maps. Hopefully 19A fixes some of these annoyances.
I will post any irregularities I see.