Palenque is an extremely important site for Mayan civilization.
Unfortunately for tourists, there's less there than the reputation would indicate.
Only 1-5 of the total site has been reclaimed from the jungle, so you can see the whole thing in a couple of hours. Unless you are hell-bent to go for the history, or are in the area anyway, it's a long way to travel for what you get. Unlike Chichen Itza or Teotihuacan and other per-Colombian sites, Palenque isn't near anything particularly interesting. The town of Palenque is mostly another sad, poor Mexican town, with a few hotels and restaurants. The archeological site is well-maintained, and our guide was quite knowledgeable, though his English was at the bare minimum level.
The Misol-Ha and Agua Azul waterfalls were more disappointing: hours spent traveling over horrible roads to sites that were nice, but hardly worth the time invested. It was fascinating to travel through rural Mexico past villages and towns I would not otherwise even know about, but the roads are in a state of disrepair and the use of topes speed bumps to slow traffic meant grinding to a near-halt dozens of times.
Better than going to the waterfalls in my opinion would be to spend some time at the Palenque Museum. Our guide discouraged us from going because he likely got a kick-back from the restaurant at Agua Azul we ate lunch at. In hindsight, I would have rather paid him a bit more NOT to take us there.
While the town of Palenque isn't much to talk about, we did have some good food at the Restaurante Maya and Bajlum, which prepares are vision of authentic Mayan food cash only!. And our stay at the Hotel Villa Mercedes Palenque was a bit of paradise in a chaotic world.