Surely you'd agree that a mouse as an interface can provide benefit even in the context of a text editor?
One thing I still find myself doing in vim is using the scroll wheel. Browsing and editing is a context switch anyway and I think scroll wheels express scrolling a lot better than keyboards ever can.
Furthermore, the fact that all my vim-context keypresses can be stored as a 'macro' in itself has provided enough of a productivity increase to make it all worth it. And this is even the case in less-than-perfect vim emulators.
And I do agree that for some things, scrolling and perhaps 'exploring' in general being a big one, a mouse can be worth the context switch.