Josh, yes, I only day hike Whitney. I started at around 3 AM and got back a little past 4 PM. It's doable, and trust me, I am NOT a fine specimen of human health.
I went up Gorgonio a few weeks ago with Microspikes and it was just not fun at all. They were worthless on steep slopes and had no bite. If I had a choice, I'll ditch the poles for the axe in a heartbeat, no questions asked.
The only place you'll have problem finding the trail is after the log crossing and nearing Lone Pine Lake. Be very careful there. Everything else is very straight forward; you would have to try very hard to get lost at any point before or after that. It was dark, and I'm not good with all the names and landmark, but once around Lone Pine Lake, and you have trouble deciding which boot track to follow, take the high ground. I made a direct bee-line and skipped Outpost Camp. Headed up the slopes, and voila, I see the chute in the distance and one main track traversing over there. I know that's lousy directions, but you have to understand I was fishing around in the dark myself. :-)