I mean, my claim to fame was a day 2 king promotion in the exhibition game. I used the tactic that Bigredsk10 suggested above to eliminate another player. It was incredibly effective.
That being said, though, I also had a few conversations with other players in the game, notably FateCreatr, where I told them, "I doubt that promoting the king was wise in the long term. It was a way to win my first war, but I've never promoted one this early," essentially. It's a tricky specialist to use well. But, if you trust your neighbors a lot, the way I did in the exhibition game, then it can work. It is a very aggressive hire, though.
"Can I make a suggestion that doesn't involve violence, or is this the wrong crowd for that?" -Hoban 'Wash' Washburn, Serenity