Purely positive here, too -- yes to all. I had everything dialled in quite well, eliminating buffeting almost entirely, and when not eliminated reducing it to acceptable levels. And then went and rebuilt my seat to move the pocket forward 4-6". Completely threw my Airflow effectiveness out of whack. Still working through different mounting heights, mirrors, etc., to get back to where I was before.
I've also used a deflector, but on top fo the Givi lower screen (upper removed), not stock. Works great in warm weather -- I can actually direct more airflow to my core -- but not as flexible as the full Airflow upper, and especially not for colder weather.
One of the big positives for me with the Airflow is flexibility. I can easily and quickly adjust it for changing conditions. I imagine stock screen + deflector would provide similar benefits, but based on my use of deflector with the Airflow lower, perhaps not as broad a range of flexibility.
For ~$20 for a deflector, might be worth trying the deflector on the stock screen. If it's not good enough, you're only out $20, and you could then get the Airflow. And you could also try the deflector on the Airflow lower in hotter month's, too.