I really really enjoy going here. It's fun for both locals and visitors. As a local, I've been multiple times and still don't think I have seen enough. Each time I go, I learn something new or am reminded of something I forgot. Because it's such a full museum, it's difficult to see it all in one go (unless you have 3+ hours to spend!).
The exhibits are done well and are engaging in different ways. The walk through is pretty easy to follow and shows a great transition from Las Vegas' history, to the history of the mob, to the growth of Las Vegas (and the mob's involvement in that) to organized crime that exists today - and THAT is just scratching the surface. There are so many missing pieces in between that we sometimes forget or aren't even aware of and the museum shows you that.
Tours are nice and very educational, but I think it's fun to walk it yourself, so you can manage how much time you want to spend on something. I would say this is fun for all ages, but due to graphic content in some areas, I am always surprised when I see young children there.
Go to the Mob Museum! You won't regret it!