Thanks to the previous messages on this board, my brother and I successfully summited Mt. Whitney in a day hike on August 7th.
Our total round-trip was about 16 hours. We started our ascent at 4:30 AM. We reached the summit at 2:00 PM. We were back down at 8:12 PM.
At our arrival to Whitney Portal at 4:15 we met a couple who had just seen a large bear at the trailhead. This bear had disappeared when we began our ascent.
Conditions were great with almost clear skies and 40-degree temperatures. The wind was a little brisk.
We walked at a consistent, turtle-like, pace and took extended breaks at Trail Camp and at the summit. This relaxed pace allowed us to complete the trip with pain largely confined to our feet. We each used around 4 liters of water that we carried from the bottom. We took an Excedrin both before the ascent and at Trail Camp. We did not experience any altitude sickness.
On the way up the switchbacks above Trail Camp were tough but doable. We had no fear of heights on the switchbacks because there are no cliffs except those protected by cables. The "Windows" above Trail Crest were, I believe, over hyped. Only the first one, at Trail Crest, offers any true danger, with steep drop-offs on either side. The four others have moderate slopes on the Sequoia Park side.
My impression is that the real pain of the Mt. Whitney hike is on the way back. The anticipation is gone. Energy is gone. Dehydration may occur. And, especially for us, the feet start to twist on the many trail rocks. The last few miles from Lone Pine Lake to the trailhead are interminable.
Along the way we met a woman in a light blue ski suit who made the summit but was having problems on the way down. She was dehydrated, vomiting, and not keeping down water. Although a day hiker, some people took her in at Trail Camp because there was no way she could make it down without an extended rest. Does anyone know whether she made it down the next day?
In conclusion, with proper planning, a reasonably fit person should be able to make it to the top of Mt. Whitney and return with no long-term pain. It's a great trip and fantastic experience.