Built this for a (casual) 1v1 tournament a nearby store does. Didn't get to run it in the tourney yet, but I played it in a 4 player and a couple 3 player games.
The four player game I got a solid start, but ran out of gas. The game dragged on forever and never technically finished, but I quit to join another game when I was at low life and behind in basically every way.
First three player game I got a turn 2 taurean mauler off a chrome mox, followed by a jitte, which closed out the game pretty quickly with the double strike bonus.
Second game, after assuring my opponents that I'd gotten a lucky start, I mulled a bad 2 lander into a 1 lander into a 0 lander, and finally kept at 5. Those five were ancient tomb + chrome mox into taurean mauler on 1, followed by sylvia and some dragons to close it out with 4 fat double strikers.
After that I figured I should probably switch to another deck
Anyway, a few things I've noticed:
Having played a decent numbers of partners before, these ones were some of the least balanced. Sylvia is quite strong, having double strike in the command zone is great, obviously, but being able to apply that to a bunch of solid midrange creatures helps close out games pretty quickly. Khorvath, on the other hand, is pretty terrible. Sylvia is a solid standalone creature, but Khorvath is way behind curve on his own. And the bonus works kind of terribly with knights, since you've probably played all of them before it comes out, so the haste is pretty minor, and flying is a pretty weak bonus for 6 mana. He's decent if you've got out Sylvia already, but still much worse than basically any other dragon with haste. It feels more like a Sylvia deck that has a mediocre mana dump late-game if you have nothing better to do.
There's a big difference between 3 and 4 player games. Honestly, Boros isn't that bad for 3 player, but adding another player makes things really hard. Obviously other factors make a big difference too, but it's an interesting feature of the game.
It's hard to find a happy middle-ground for aggro decks in the format. If they're good, it's pretty annoying - after the games with this deck, I borrowed an ur dragon deck and played against edgar markov, who killed me the turn after I played my first creature. Boros being bad is kind of an intentional part of the format, like it or not. At least, as long as it's aggro.
Anyway, I'm pretty sure it'll do nicely for the 1v1 tourney I built it for. Powerful but off the beaten path. Less than 100 decks on edhrec, that's gotta be among the lowest for partner commanders.
It was a little silly. The tourney was low turnout (only 6, usually it's 10 and caps at 10). I was kind of nervous that a boros deck wouldn't be able to hold up to some of the big value decks like animar and meren, but it won fairly handily. The only game I lost was when I got stuck on 3 lands for 7 turns or so.
I would describe most of the decks as being heavily synergized around their commander, lacking in answers, and bad at coping with enemy answers. I won most games where I was able to kill the enemy commander once. Also I kept drawing Ancient Tomb in over half my games, which was an absolute all-star. Having a T2 Sylvia with any equipment to follow up was basically unbeatable for any of them. I think I only cast Khorvath once. Poor guy.