The weapon is my second favorite in the game, the alternative fire is awesome, deals 50 body shot and 75 headshot, that's the only fire I use pretty much.
The cacodemon is my favorite demon out of all. You can freely fly all the time, you have close quarter wall hacks when you hold mouse 2, which is the mode to glory kill enemies with your tongue hook if they are close enough (the range is awesome so don't worry), mouse 1 is ok, deals around 55 damage on direct hit but you'll spend most time holding mouse 2 to get the wallhacks and instant kills.
Armor parts are alright and the color pallets are not that great.
The patterns are shit and the taunts are alright, there are plenty of funny taunts.
Overall the only dlc you should have to pay full price, but of course 15 bucks is rediculous for a mostly cosmetic dlc.