I just read the entire thread, and all I can say is WOW. I am sorry for those who are having so many issues.
Here is my comments:
Lumia 1520 (AT&T)
Running fairly stable, so far. I had 1 random reboot today at around 14:00, but otherwise not bad. There are a few issues that I see constantly, and have reported via the feedback app:
The start screen background shifts left after about 1 hour. It can be reset, but occurs over again
Saved images from internet explorer or project Spartan do not save to the phone or SD card after long pressing and choosing save image
Although enabled, saying Hey, Cortana does not have a result
Like many here, tapping an email notification results in the Calendar app opening
Otherwise, all is well. I will update this post if I find more issues.