Definitely worth seeing if you can take a few hours to pull yourself away from the Las Vegas strip.
We didn't do a tour or take one of the bus trips - we went on our own and we went early in the morning, which I highly recommend... parking and even walking across the dam become extremely tight as the day goes on.
It was a great site to visit and I'm glad we saw it. I wasn't amazed or knocked out by the significance. I WAS amazed that you have to pay $10 for entry into the Visitors Center. I've honestly never heard of anything LIKE that... On top of the $10 you'll pay to park. Parking - OK, I understand. But a fee for a visitors center? Nope.
Anyway, see it if this is your kind of thing. Go early. And there are some good places to stop for breakfast on the way - so have fun with the little side trip!