Lumia 1520 AT&T (unlocked)
I upgraded to 10586.11 from 8.1. I reverted back as I have been in Europe for two weeks and needed total reliability.
Upgrade went smoothly. A few store apps stuck, but were fixed with a soft reboot.
Currently, the only problem apps are Network Services and Rate Your Device. Both return the 0x803F8006 error.
Neither are important, so I am ignoring this and enjoying a very nice, smooth OS that is running well!
Let me add, that this upgrade kept more of my settings intact than any other. I have had to do less "fine-tuning" this time compared to previous upgrades. This makes sense, of course, since most users will be coming from 8.1
If you are having troubles, restore back to 8.1. Get all your apps setup the way you want. Wait and let them update, etc. This can take a day or more. Once everything is just the way you like it, do a backup, install the Windows Insider App, click Fast Ring and go for it!
It certainly worked for me!