I had them, Caltracs helped with wheel hop, the traction was horrible with or without them (with street tires), BUT, I've heard that with slicks its a different story, very hard launches.
The other thing i noticed was that with the caltracs, even when the tires are spinning the truck rides straight, and , without the caltracs the truck slides from side to side without any control.
Hope this helps.
STOLEN: 2005 SILVERADO 1500 4WD ECSB 5.3L 3.42 gears
Sold: 2003 SILVERADO 1500 RC STEPSIDE 5.3L 3.73 gears