My wife and I are in our late 50's (ouch!) and have done the half dome hike twice. The first time it was an "up and back" from the valley floor. We left at 6am and got back at 5:30pm, spending an hour at the top and another combined hour hanging out at Vernal falls, Nevada Falls and the Merced River at LYV. We used hiking sticks, took ibuprofen, drank lots of water along the way and ate granola bars, trail mix and other light foods. We trained for 6 months by hiking all the local hills on a weekly basis, looking for about 3 - 4 hour hikes. The up and back hike is certainly doable with a little preparation, or at least a little youth.
Our second trip was a backpack trip where we spent the first night at Illouette Creek and a second night at LYV. From LYV we hiked to the dome, leaving at about 6am and getting back to LYV at about noon. We left our gear at LYV and just took, sticks, water and snack foods with us. Once back at LYV, we packed up our gear and hiked back down to the valley, again stopping at Nevada Falls and Vernal Falls for rest and relaxation. I think we got down to the valley at about 4pm or so.
Overall I enjoyed the backpack version more than the up and back. I go backpacking two or three times a year and have the gear to do it, so its easy for me. Granted, hiking up the falls with a backpack is tougher than without, but you don't have to travel as far, so in my opinion it's a wash. The benefit of backpacking, assuming you're leaving from LYV, is that you can get to the dome much earlier than the valley crowd. Even with the new restrictions, the cables can get pretty crowded starting around 10am or so.
We are going again next weekend and are doing the backpack route. I got a wilderness reservation from Happy Isles to LYV, leaving Friday. When I pickup my wilderness permit, I'll also get a half dome permit for Saturday. We'll hike up to LYV on Friday, do the half dome hike Saturday, spend another night somewhere out there (maybe along Sunrise Creek) and pack back down to the valley Sunday. What could be better?