Rolled my 520 back to WP8 yesterday, glad I kept my 928 on it. Will be interesting to see how long it takes for non updated WP8 phones to become unusable, due to outdated apps/integration (FB, Twitter, Sky/Onedrive, etc).
Edit: as for expectations: no, it did not meet mine. I expected upgrades, not a complete rewrite and abandonment of so much that drew me to the OS in the first place.
Hubs could have been redone in a way to allow upgrading, instead, they abandon them. They use their metrics to say people passed through the pictures hub on the way to look at the camera roll or other albums -- their metrics evidently did not include the pause and the smile that many people enjoyed seeing a favorite as a panoramic background. They redid the phone app to make it less smart, to make it more like my wife's flip phone, and removed obvious UI clues (circle phone icon for dialing) in favor of an action with no obvious clue that is not the same elsewhere (tapping the name). They rammed the status bar down our throats after telling us just a few years ago how we didn't need to have cellular, WiFi, battery, staring at us all the time -- I don't need to waste my time with that stuff. They went backwards in time, and not only didn't give us folders in the app list, they flooded it with games. Just a few examples. Not bugs, bad design.
Plus sketchy performance overall, well, after standing there tapping my non responsive 520 like a bargain basement Android phone, I realized I needed to roll back.
And don't think Cyan will magically include "drivers" for better performance -- these things all run on the same chipset, it may include a couple Nokia tweaks for camera etc, screen brightness, but performance and battery won't be changing significantly. This thing is live in the wilderness already, there aren't any major fixes coming either.
Sorely disappointed.