F'ing awesome for me! I had a annoying highway vibe that I couldn't shake and it cured it. I went through two OEM shafts having both of them balanced and the vibe wouldn't go away. I put a PST in and it went away and was smoother than ever!
Other than that I would just stick with a stocker..... There expensive!
I'm also considering one for this exact reason. I have a driveline vibe that's just enough to be annoying. I can't decided if I want to even bother with trying to balance the stocker or just take the hit and go CF.