I've actualy had a hard time with the Gunpowder tree. I just can't seem to deal with everything as effectively as I do with a decked out Gurrela tree. Maybe I'm just too lazy and over-rely on my turret to do the hard work.
Though there is something immensely satisfying about dropping the turret on a group of skags or varkids, and strolling away as they're annihilated without you ever having to fire a shot.
"How're we doing?"
"The dwarf's on fire."
"So as bad as usual, huh?"