(Reuters) - Walk softly. Global growth looks to be smoothly downshifting as China slows, the U.S. economy firms, and troubled Europe, at least for now, avoids a messy crash. Ratings downgrades on nine euro zone countries by Standard & Poor's late Friday - including France, Italy and Spain - sent a shiver through financial markets. But the move was long telegraphed, likely limiting any spillover. A global economy slowing only gently would be an immense relief after a fraught end to 2011, but it is far from guaranteed.