This is an awesome idea, I just installed and tried it out. A few things jump out at me: if you have fifty tabs open, the first use experience is a little painful--you want to be able to create workspaces and quickly file things away, but it's a very slow process. Opening a workspace pops you into a new view, and it's not immediately obvious what to do from there.

I get that the first use may not be the case you're optimizing for, but it was a bit frustrating.