I really enjoy this hike/walk. As Norm pointed out, there are several options to make this trail "do-able" for everyone.... short version or long version.
It's a great trail for leisurely walkers.... for runners... for bikers... for families with kids... for dog-walkers....
Plus, you get some lovely views of Lake Mead as you walk on a historic trail and feel the history around you.
What's also great about this trail is that it is mostly in the shade.... so that in the summer time.... (if you go in the morning).... most of the trail is in the shadows so that you don't easily overheat.... and the tunnels are cool at all times of the year.
Note: there are no water fountains along this trail so bring your own water if you want to hydrate while walking.
There are benches so if you need to rest or ponder the meaning of life.... you can sit down and relax for a moment or 2.
Plus, it's super easy to get to.
(And their are restrooms at the parking area.)