You may find more information by searching on the web, but i will give you my objective opinion. I did bug him about fabbing me a kit for the Trooper and VX, but never followed up. Since I woke the barn queen up for the dyno run ( I drive 1 hour each way to work everyday, and cant afford to drive the VX as a daily driver anymore), I may have him do one.
A grounding kit especially an aftermarket one will actually allow electrical accessories to run a little more efficiently and therefore draw less current. Some people would also argue a hotter spark in the combustion chamber due to the electrical efficiency that is added. If you have an aftermarket stereo you will know the importance of a good ground with an amplifier. Ground actually determines the power, quality, draw, and or excessive heat due to electrical demand that is asked for by the amplifier. This is especially important on aged vehicles since there is corrosion that limits the original grounding straps from providing a good ground. An old timer method I used to use was to remove and clean the bolt, screw, etc. Clean the contacts, and spray WD-40 on all ground strap contact points to try to prevent this corrosion. Some automobiles do not have an efficient grounding system from the factory anyways. This is an engineering and/ or cost issue. These types of vehicles do see a performance difference albeit small. Mostly smoother running accessories.

The decision to use a grounding kit is speculative from one vehicle to another. Eye candy under the hood? Check. Peace of mind because of proper grounding for years to come? Check. One less thing to worry about because of some diagnostic investigation you may be performing? Check. Possibly at the most a 2 to 3 horsepower gain on a factory insufficient ground? Check. Less corrosion due to quality less corrosive materials used in the system? Check.

Also, one other thing to consider is the cost. This is one thing that can be done for a less substantial amount of money than just about any other modification. I would rank this mod about the same cost/ benefit as a breather/ pcv valve catch can to keep oil fumes from gumming up an intake and throttle body, or upgraded spark plug wires, or even synthetic fluids for less viscosity, protection, and less wear.