dear hawk37,
supercrit wings serve to increase the Mcrit so the aircraft is still flying somewhat below this speed. a typical margin of .2 (no turbulence expected) to .3 (normal) G is maintained by the Mmo with respect to the high speed buffet and cruising speeds are lower than this. typical cruise speeds are well below high speed buffet, except when operating very close to max altitude for the weight.
the need for mach trimmers seems to be more of a certification issue on many modern airliners, though i daresay there could arise (not normal) situations where they could save the day.