For me, Siri will be handicapped by my having information in multiple ecosystems, walled from each other: 23 years of email in Gmail, Apple for files, messages and Maps, Office365 for work and Claude knows quite a bit about me. I suspect many users will face a similar problem.
Vivaldi is my default browser on Mac, and has been for a couple of years. Great tab management, including groups and tiling, as well as a command palette. Chromium-based so you get all those plugins. Supports hiding tabs, address bar, toolbars and other window chrome (lowercase C), which is great on a 13-inch MacBook.
That’s going to be a real issue for people. Hopefully Google and Microsoft build indexing into their apps quickly. Google Drive + Gmail, and OneDrive + Outlook would be key