Well I can't really tell you because I installed it over my 8.54, so my visual preferences are as before..
But meh, they changed the new window shortcut to Control + N (previously New Tab), and that's the only difference I've found yet (apart from the new features like the widgets).
By the way, you can change the shortcuts on Tools -> Preferences -> Advanced -> Shortcuts
Differences :
1 - Changed new tab shortcut
2 - "Sneak-Peak" of a tab when you hover it, with several information and a screenshot
3 - Different 'About Opera' webpage
4 - Source Code opens directly on a new tab and not on Wordpad/Notepad
5 - To use BitTorrent through opera you simply have to open a torrent with Opera and follow the instructions
6 - Content Blocker (Right click on a page -> Block Content)
Works quite well!
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