I absolutely love vivaldi and switched a few years ago, probably 2 years ago, so I've used it enough to really know it's for me today and not 2 months then gone back to chrome after problems. I had major annoyances with its default settings (omnibars mostly) and it throws opinionated stuff at you but its customizability is incredible and once I fixed the omnibars annoying default search settings I was good. It defaults to any typos or wrong domain names taking you to startpage searches and its frustrating for new users but you can turn it off.
Drag and drop tiling into the same window instead of having to create a new window sold me a long time ago but I also have tons of other customizations. But then you have the vivaldism where I can't open a new window and drag a link into it because because the start page captures that as a page add. It has some hiccups but in general I love it.
As an example instead of ctrl+n'ing 4 windows side by side and having to add all the additional window padding a new browser window vs tab has, you can sit on amazon or whatever retailer and price compare 4 tabs right next to each other in the same window and there is almost no padding taking up room, etc. It's very clean, you just drag a product tab into the same window and it pops into it as a tiled page that you control separately, and its marked with a highlight. You can tread the tiled page as a new tab, but its much smaller and you have to click it inside of the tab, so it's not something you're going to drive all day long. I'll put 4 products next to each other, read about them then close it or use that tab as my research tab.
Built-in full page screenshotting/exporting way better than Chrome. I haven't used the mail. The sidebar takes getting used to, I use that as a favorite bookmarks bar and look at downloads in it and RSS feeds. Built in vertical tabs I never look at that. Its sync is much better than it was a year ago, I've had no problems, it's not google chrome sync but you just throw a code onto both ends, my android vivaldi doesn't have extensions unfortunately.
It has an insane amount of settings that I spent a few days tweaking and sync between everything, and now I never touch that menu it's frightful. Sometimes I have to edit my right click context menu because Vivaldi decided to move a button under something (hello, close all tabs to the right). But you CAN do it vs other browsers that don't have full UX control and I'm now stuck with Googles (maybe) decision to hide my right-click close tab button under a 2nd dropdown.
It's been basically a chrome experience in that I don't get errors and ever have to use chrome or safari/bingthing basically ever.
I was always a heavy chromium extension user and customizer, never clicked with opera and firefox runs me off by some business decision every few years, burnt me migrating profiles, etc. I may have to hop off the chrome train completely though.
Whatever I pick next will feel ancient without vivaldis drag and drop tab system.
I haven't yet but eventually I'll happily donate $20 to the project. It's the first time I've felt in years like a browser was actually doing something new.
https://help.vivaldi.com/desktop/tabs/tab-tiling/