Naci is fun lake. Most of the party action happens back in "the narrows". The lake itself is fairly narrow except where it opens up before turning left into the Marina area (from Oak Shores/Christmas Cove). Watch out for debris at the surface of the lake. Early in the season when the lake rises from the rain water, there tends to be a lot of branches and stuff that collects into the lake. Also, watch out for under water rocks. Depending on the water level there can be rocks in the main portion of the lake that can do damage. Most are clearly marked, but if you are new to the lake take it easy speed wise until you have driven it at least one time.
The lake itself is very fun and the crowds in "the narrows" can rival that of copper canyon/steamboat/sand bar at times. Definately worth the trip. The setting is much different than Havasu.