This is a pretty difficult hike -- the trail includes a lot of steep uphills and precipitous downhills, with some clambering over rocks. It's a challenge! But beautiful, especially at the top, and very isolated; I didn't see another soul for the whole hike. Chimney Top really does go right to the top of the mountain, up, over, and around the rocky summit. I can confirm that the Mart Fields campsite does have a water source, a hundred yards or so down the Chimney Tops trail -- but when I was there it was a meager trickle. One note: they have moved the Chimney Top trailhead so that it comes out by the Visitor's Center, about 1/4 mile down the road from the Spicewood trailhead. So the last bit of the hike is along a paved road (but one with very little traffic).