Saints Row developer Volition loves Johnny Gat. Saints Row fans, in general, like Johnny, but Volition loves that psychopath, and it's been trying to share the love for three games now, only to have him overshadowed by the gang of puckish rogues we know today. In that way, Gat Out of Hell was almost a foregone conclusion. Johnny was always going to get his time in the solo spotlight and all Volition needed was a good excuse to get that band of rogues we've come to love so well over the last three Saints Row games out of the way so it could happen.
The irony is that when Gat Out Of Hell succeeds, it succeeds around Johnny, not because of him. He is more of a cipher than the player-created Boss. That's not because he's a bad character--he is slightly one-note here, and the storyline isn't doing the heavy lifting it does in the main game--but because Volition's obvious focus on world-building in Gat Out Of Hell is so strong. Virtually everything else small and character-based suffers as a result. This isn't necessarily the add-on you buy because you're looking for some sense of finality from these characters--How The Saints Saved Christmas actually managed to do more of that than anyone could have expected. You buy it because you're looking for one last jolt of wild, unhinged chaos from Saints Row in a brand spanking new playground, as the series as we know it moves onward and upward. Gat Out Of Hell delivers that, but it could have delivered so much more.