I've never used a tweak station on a 1/12th scale. Best to use pennies on the front tires.
As far as if they are good or not... I use one, but a couple of the pros at my track do not. In fact, if you put their car on one it looks totally tweaked. The reason is, they set the tweak on the track, and the tweak board cannot compensate for the torque steer the TC3 has. This is most notable in mod. I've not yet mastered setting tweak on the track, but I'm getting there.