Sweet, didn't know about the new change in Minefield. Thanks for the heads up!
Firefox 4 (out-of-the-box and on the surface) is going to look more and more like the current Chrome. A new breed of Firefox extensions will surface very soon to hack away a lot of ui stuff back to 3.6 (Namoroka) branch. ("classic" status bar, "classic" tabs, things like that...)
That's not the status bar, it's a couple of toolbar buttons dropped on the right side of the tabbar. Minefield doesn't have a status bar anymore. It's renamed to "Add-on Bar" and is used only for placing addons' icons.