Per comments on Mt WHitney Facebook group:
1) Father and son team - successful summit - standard route.
Said switchbacks not usable, used crampons and trekking poles for the chute.
2) A different climber ascending same day mentioned she saw the switchbacks being used by a "few" people, but the majority used the chute and glissaded down.
3) see hiking report from Guitar Lake to Whitney summithttp://www.hikinggeek.com/2015/08/07/hig...owU5Fx0slRIgjCE