This is how DLC should be like
This DLC features new vehicles, weapons, and even parachute jumping challenges. The story is quite entertaining, in a usual Rockstar kind of way, with lots of weird characters and funny dialogues. The story also does a great job of crossing paths with other two GTAIV stories.
Once you finish the story, all missions can be replayed through options find on your phone. Each mission has certain optional challenges or requirements to meet, such as scoring a certain number of headshots, finishing a mission in under a specific time etc.
If you liked GTAIV, you will love The Ballad of Gay Tony, it's one of those rare DLCs that are actually worth the money, because its length is like any other full game released today.