Janine, be sure to check the Trip Reports forum (scroll to the top, click Forums, then Trip Reports). There are two good reports, one by Michelle, a second by Gregory.
Most people's experiences are somewhere in between those two. Michelle, from London, UK, made it in one day: 5 hours to Trail Camp, 2 more to Trail Crest, 1.5 more to the summit, 6.5 to descend, and she says she rested little!
She spent two prior days doing some acclimating hikes, one hiking the Main Trail up to Lone Pine Lake and back -- a good thing to do in daylight, if you are going to day hike starting in the dark.
Gregory, on the other hand seemed to lose the trail often, and his labels of places don't match the map. In fact, the Mountaineers Route is not even in the area he was hiking. But one of his biggest mistakes was to underestimate the affects of the altitude.
Also, be sure and look over the Orientation Notes (link above on the left). There is lots of useful info tucked away there.
