The spatial organization thing looks pretty novel to me.

Tab groups do that, unless I'm missing something. Probably not as good, but again, why do an entire browser?

Because, looking at the demo, it can do a lot more than what you can achieve with tab groups…

Could you mention what? As they said, the shortcut to bring to front is OS configuration and spatial organization is in tab groups addons (though without arbitrary spatial locations), and the fuzzy find seems similar to what Vimium provides. I'm open to the idea that there's value in grouping such features together - but unless I'm missing some other feature, this seems much better implemented (and has a better chance to be long term supported) as a Firefox profile with those addons installed and perhaps a tiny program to capture the shortcut and execute that Firefox profile.

Yes, but cound't you make an add-on that does those additional things? Or a service? Or both?