Yosemite is the type of place you don't really want to leave once you've gotten there. First there's the scale of everything, from the Giant Sequoias, to the waterfalls, to the cliff walls. Then there's the beauty in every detail, from the moss and lichen giving stones distinctive patterns to the flitting shadow of a deer or bobcat. You could probably spend a month straight there and not run out of things to do (although I think more than a week or two with small children might drive you batty). The weather was warmer than normal, around 70 degrees every day, and we hiked about as much as you can with small children in tow.
One day we hiked to the top of Vernal Fall. It's only a mile and a half from the bottom to the top, but much of that is more or less straight up. Vernal Fall is beautiful, a thick long sheet of water plunging onto huge chunks of raw granite and throwing so much spray that the upper part of the trail is called "Mist Trail." At that point you're climbing wet rough cut granite stairs and if you're me you're reminding yourself that you're almost there and damn it'd be a shame to turn back now even though you really really want to stop climbing.
You do eventually want to keep climbing, though, because you know you'll get to the top and once at the top you won't have to do anymore climbing, you'll get to sit down on a big slab of rock, close your eyes, and listen to the water rushing. You can also stand at the edge of the fall and look down into the valley below:
In the bottom right, you can see the water as it begins falling over the edge. In the lower left you can see little dots of people climbing along the trail as it winds up the mountainside. Other hikers were lying in the sun, resting from the climb, eating their lunches. Like us, many of them would be turning around to head back down the trail after a short rest, but some would be continuing up the trail another two miles to Nevada Fall. We saw a pair of hikers coming the other way with cross country skis strapped to their backs; outside the valley, there's still snow on the ground in places and many of the high trails are closed because of ice.
It's much easier coming down, by the way.