so I take it you haven't had one ? yet can offer an opinion
Nope, I can't see the point in £90 of ugly cables of which no one can offer conclusive proof it does anything at all. If you give it even half a google, you can see that tens of tests have been done on a range of cars and forums, and the answer is always the same, 25% say categorically no, 25% say categorically yes and 50% say I like the look of the cables so I don't care. How many timeattck/drift/drag/track day cars running the standard engine do you see with an earthing kit on? I don't recall seeing any, because they all keep the standard earth points in good condition which means they don't need 200 metres of cable. Granted, some uprate the ECU earth points if they run an aftermarket one.
It's like those bracelets people wear with magnets in to "aid recovery" proven load of tosh, but millions of people still buy them.
Show me some impartial evidence showing the awesome benefits of a grounding kit, which aren't based on opinion and demonstrate that the same result wouldn't have happened if you'd cleaned/renewed the oem earth points, and I'll happily buy a kit for £100 and fit it tomorrow.