Anyone have one of these or heard of one? I was thinking about getting one but I did not know if it was worth it or not.

http://www.slipstreamr.com/HGS.asp

 

Grounding kits are most effective if you have a high electrical load on the car, and/or are trying to eek out every last bit of power. Generally though, you can clean up the stock grounding cables and clamp points to regain losses you might incur from a bad ground.

So basically, they don't hurt, but aren't absolutely necessary, which ultimately means: it's your money.