I have 6 profiles that I like to keep separate, and the only browser that supports seamless switching in the toolbar is Chrome. That's the only reason I continue to use it. If Firefox were to implement this, I'd immediately switch. I know there's addons that try to simluate what Chrome does, but they just aren't as easy to use and don't do exactly what I want.
I have. It simply sorts tabs by profile, rather than sorting whole windows. Think about it this way: I want to have 6 separate instances of Firefox running at the same time, where I can seamlessly switch between them. Each instance has its own theme, bookmarks, cookies, etc.
Firefox can do this, but it's not intuitive and it opens 6 different Firefox apps on my Mac, so it isn't easy to distinguish between each profile. On Chrome, I simply click the person switcher at the top right and I can switch between sessions very easily.