Sidebar design done right

I'm not usually fond of Microsoft's UI designs, but in the case of MS Office 2003 products, they've outdone themselves. Look at this example of easy navigation between different sidebar options:

Now compare this to how it looks in Firefox:

The search bar is a nice touch and somewhat redeeming feature, but having fast navigation between different sidebar options would be even better!

Update 24/04/2006:
The All-In-One Sidebar Firefox extension looks like a good alternative solution, although I've yet to test whether it will accommodate Document Map, which, to add annoyance, is broken in the current Firefox release (1.5.0.2).