I just ran Narue's test on my XP, 2.41 GHz AMD Processor, 1 Gig RAM and pretty fast video card.
compiled with Visual C++ 2005 Express editiion in release mode. One problem with such as test is variance in speed of hardware -- you will get much different results with different video cards and processor speed. That alone will invalidate any such speed difference tests.
Using Microsoft compilers, I am not at all convinced that std::cout is faster than printf(). I have made similar tests in the past on other computers with M$ os and have never seen one where cout is faster than printf(). And I would be supprised if *nix computers was any different.