If you can get a good used one and a controller, it is a good way to add another gear. I have a 93 G-30 van with a 6.2 and 4L80, works fine. If I stop using the van, that tranny will probably end up in one of my CUCVs.
The gear splitter is an interesting concept, not that I would go for the expense. I suspect some of the '6 effective gears' are in between the lower ones, not on top of them. Like a split shift two speed axle, if anyone is old enough to remember those, you can keep the engine closer to its optimum torque curve during acceleration.
edit; I think you could find this swap discussed quite a bit in older threads.