We still install terraces here, but, they are generally done to intercept water before it begins to form a gutter.  We do it to eliminate waterways up every draw in a field.  One waterway for an outlet and a terrace across the other 1,2,3 draws in the field.  Works well for the small watershed we have here yet still have gullies form.  Your drainageways can have 10, 20, 30 acres with no discernible erosion.  Gotta love that limestone!  Our crappy county where shale and clay prevail along with many hillside springs: a 3 acre watershed can develop a serious erosion gutter quite easily.  I will say that "HERE" no-till and cover crops will not replace the need for waterways and other surface water control practices.  Don't get me wrong, my goal is for every acre in the county to be no-till and cover cropped, but, I know that some surface water controls, as well as subsurface water controls, are necessary.  We have probably installed more waterways through the EQIP program than any other county in the South Central Region in the last 10 years.