I'm pretty sure there's some form of ABP either in existence or on the way.
Multiple occurrences of the same browser engine in the one window? Why?
And I don't get the last one. I hate these ancient 'battleship style' UIs that IE and Firefox have. With Chrome, you get the same optionality in two drop down menus... Why do you need more?
Chrome has an "ad-blocker" which is essentially an ad-hider. Due to the constraints of the plugin API currently, they can't make a plugin that actually stops the ad from being requested. All it can do is hide the fact that it actually did get the ad. So it looks the same on the surface, but bandwidth wise, it isn't.
Split browser is handy for comparing things side by side with no window borders to worry about. You can do a 4 way split if you're so inclined and not have to fuss with resizing one window when you resize an adjacent one. It's not a feature many would use every day, but it's nice to have the ability to do. And that's the beauty of Firefox's current level of extensibility. If you want to do it, you can, and there's probably already a plugin to do it for you.
As for me? I cant live without a tab tree, and Chrome doesn't have them, or even the ability to do it yet. I can have dozens of tabs open. Heck, during research periods, I can have well over 100 open. A tab tree allows me to keep my browsing history easily navigated. And no, bookmarks and other such workarounds don't cut it. I can switch between tabs with no delay and be exactly where I need to be on a current page. Hell, I can have the same page open in two tabs with each focusing on a different part if I so choose. Tree tabs + session management = bliss...