I've heard it; it's hilarious. But then I think Led Zeppelin were hopelessly overrated.

More here:

http://www.spinnermusic.co.uk/2010/02/03/mary-j-blige-stairway-to-heaven...

I don't have any audio or video for you at this point. But bloody hell, it's funny. The sound of a sacred cow mooing loudly whilst milked.