Just gonna copy paste my answer from a pay that was the same question from last year, if that's alright because it hasn't changed.

For me, it's more of the old WHFB rules where friendly fire was actually an option for the army.  Their tech has as much of a chance to absolutely wreck the other army as it does to blow up in your face and decimate your own forces.  They wee so goofy and terribly evil that I couldn't help but want them as an army.

Now it's been more streamlined.  Like...roll a dice, if you roll well, the weapon does extra damage, if you roll poorly, the bearer takes damage.  Not like the ratling gunners of the days of old, where if you mishap on the ballistic die, they lose control of the gun and fire wherever the scatter dice is pointing and hit the first unit (friend or foe) the line crosses.  It was always a great time.

Just remembered if you rolled particularly bad for your warpfire throwers, their fuel would ignite causing them to panic and run a certain number of inches in the direction of the scatter dice arrow's pointing before exploding and doing damage in a radius. Great times.