Sorry for ignoring the thread )

Was it a standalone installation? It wasn't.

At first, I thought that opera messed up with win10 UAC somehow, preventing the user data to be saved properly, but I don't think that's the case. It saves some of the preferences, after all, and the speed dial isn't completely lost, just reset to default on restart.
I guess, the issue was in the way opera syncs the user data with the account, because when i was logged in and sync was active it did not happen. But when I turned the sync off and deleted the sync data, the browser restart was fine, but on PC restart I lost it again. So, maybe the user settings are somehow being saved as a sort of temp data, so everything is purged on restart.

Anyway, I upgraded to beta and have kept opera sync active so far, and it solved this for me.

Today logged off opera account, turned of the sync and deleted the sync data. After PC restart nothing lost, opera is doing good by now. If anything changes, i'll post here.

Opera 37.0.2178.43, win 10 pro x64 build 10586.318. After auto-update I lost all my settings, themes, extensions, speed dial. History, bookmarks and passwords stayed untouched, fortunately. I restored it all just to loose again after browser restart. And it happens every time I restart opera. Seems like the settings aren't being saved. Opera saves speed dial page as a folder (even the empty one) "desktop-*****" in "other speed dial" section on bookmarks page every time I exit the browser, so I don't loose it completely. And downloaded themes are still present, just reset to default on restart. But the extensions and settings are lost for good. I reinstalled Opera (cleared the register in process, appdata folders were empty) end it happened again. Sync was turned off, opera profile - not logged in. This starts to annoy me already. And I kinda don't know where to write, 'cause I didn't find any "contact tech support" button.
Any suggestions?