We only hung around the top for about 40 minutes before heading down because we wanted to make it to the bottom before darkness set in.
It looked much more frightening going down the cables than going up but it was easier going down, much faster. I kind of repelled down sideways, sliding both hands down one side of the cable, and keeping my eyes on the ground immediately ahead of me.
On the way down, we took the John Muir Trail, a longer but less steep trail than the Mist Trail. Here, we were able to get a spectacular view of Liberty Cap and Nevada Fall. On our way up, we switchbacked up that pile of rocks to the left of the fall. This section on the way down was incredibly monotonous, with about a million switchbacks from the top of Nevada Fall to the bridge a mile from the trailhead.
It took us exactly 6 hours to get up and 6 hours to get down. We took a long break at Little Yosemite Valley on the way down in addition to the 40 minutes spent on top of Half Dome so it actually took less than 6 hours to make it back down. About half an hour after we returned (7pm), darkness closed in.