Speaking as a frequent visitor, Enchanted Rock is in fact one of the coolest places on the whole damn planet
. Big rocks are simply very cool, so an INCREDIBLY, UNBELIEVABLY, LARGE rock
is exponentially cooler.
In addition to hiking to to the top of the rock itself, which is quite invigorating, there are miles and miles of trails through the surrounding wilderness. Also, at the top of the rock is a medium length cave (actually a very large fissure) that you can spelunk through if you so desire.
If you decide to do so, I recommend you bring at least two flashlights, and be VERY alert for snakes. While encountering poisonous snakes is rare, they are out there, and you do not want to screw with them. Imagine finding a snake in your bedroom in the middle of the night. That is how a snake feels when you come lumbering through his subterranean abode. Remember kids, when you play games with venomous serpents, NO ONE WINS!
For some real fun, I recommend hiking around to the backside of the dome, and climbing the rock from the rear face. This is a much more strenuous climb (and more dangerous; if you are unsure of your abilities, or afraid of heights, I do not recommend it), but much more rewarding when you reach the summit.