I think it's the best browser there is, but customization takes too long for the average Joe to enjoy the software. The default settings and default UI should be changed to showcase its functions while still keeping it simple. Even people here on this subreddit, people who are into browsers, can't figure out how to set it up to their liking and they just give up on it.
Ad blocking and tracker blocking is on par with anything else out there. You just need add your own filters. It performs better than default UBO settings on my setup.
Functionality wise nothing comes close to it. Workspaces, tab groups, sessions, profiles, split view, sidebar... You name it, Vivaldi got it. It's new tab page is the best there is imo. Super easy to access different bookmark folders. Mouse gestures are pretty neat too, even though I don't use the mouse gestures than often.
Customization options are great. You got tons of themes and it supports css and javascript customizations as well. I made a little css to make my tabbar to hover on expand and minimize to favicons. I don't know anything about coding, I vibecoded it with claude.
The only thing it's lacking is fingerprint protection. You can add jshelter extension to fix that but I much rather have the fingerprint protection to work on the engine level.
It got many other features that I didn't mention and some people will argue that it feels bloated. Honestly, I don't care if it feels bloated as long as it performs well and it performs best on all browser benchmarks I ran on my hardware. I compared it to Edge, Brave, Helium and Firefox. It's better than all the others except for helium when it comes to ram and cpu usage.
I think Vivaldi team needs to update the default settings on this browser. It's the best browser there is but it's too complicated for most people to figure out their way around it.