The pool at the end is the payoff. The scenery along the trail is OK. The pool was closed to swimmers when we went, it gets shut down for safety at times. The pool and waterfall area is well worth the drive and meh hike. Local BBQ institution, the Salt Lick is on the way from Austin, highly recommended as a feed stop.
The hike is quick and easy, but it is a bit slippery if you're not in sneakers (my mistake). The grotto is breathtaking, it looks surreal, and the water/waterfall is so beautiful. Check the weather before you go, if it hasn't been rainy you could possibly go swimming! I drove from Austin to Dripping Springs which was about a 45-minute drive, it was so worth it.