This is an AWESOME day trip to do with friends and family when they are visiting.
We have gone a couple times and it was really a pleasure.
We had decided to not do the "official" go inside the dam tour, because it is pretty expensive. ($30/ea.) so I cannot say if this is worth it or not.
The one thing you DO NOT want to miss is the "Mike O'Callaghan - Pat Tillman Memorial Bridge" walking bridge before you get to the dam! This is AMAZING!!!! There is a little parking lot before you get to the dam, with stairs going up. GO UP! Trust me you will not be sorry. It is a spectacular walk across! The views are breathtaking. This is free, BTW.
The head down to the dam. You will need to park in the pay-2-park area to walk around. It is not much. I think $10 a car.
Insider tip: There are yummy soft serve ice creams in the little booth window at the base of the parking stairs. (not not the gift shop) - A Hoover Dam walk, with a a soft serve ice cream is perfect! Slurrrp!