Actually been here a few times, usually related to Vegas trips.
The first time was a bus tour from LV that went onto the Grand Canyon.
You were a bit rushed so they could keep to their schedule but you did get to see it, albeit briefly.
The second time was also on the way to the Grand Canyon. This time we were driving and were able to enjoy at our lesiure. The bypass wasn't open then and it was early so we got free parking and the dam wasn't too busy.
This is a true feat of human engineering. Well worth a stop to marvel at the sheer grandness of it all. Not sure if it an irban legend but I read that the concrete hadn't all set yet because they used so much and it's just so damn big!
Allows you to cross time zones as well. lol
The most recent time was after the bypass was open so it was a drive by which made the trip much quicker. All in all - great.