In our vey large (C/C++) solution, removing the Navigation Bar made typing speed in the editor go from one character approx. every second to normal.

This also speeds up the time it takes to initially load large class files, especially in C#, and especially if there's lots of nested classes.

I've always disabled the navigation bar. I'd rather incremental search the function.

On a side note, why isn't the Nav Bar a toolbar, so it could be moved to the bottom of the window? I'm sure there are deep historical tech reasons, but a lot of those quirks went away in 2010 - is there another reason?