AFLM, typically you don't need snowshoes or crampons on Whitney.
on the main mt. whitney trail, hikers were reporting use of crampons and ice axe at the end of june this year (2010) and others were still turning back due to snow and ice in the "cables" section the first week of july. this is not unusual for whitney's main trail.
you've only got (maybe) 1/2 mile of snowpack on the entire Portal to Summit route.
from october/november to july, roughly, the north-facing 99 switchback section - which contains the "cables" section - of the main trail is bypassed due to snow / ice. the 'winter' route goes straight up the chute to the right of the switchback section. ice axe, crampons, and intimate knowledge of their use is mandatory for hiker safety. people have died in that chute.