I purchased one of the first cases of Spiders that they produced. Here is a link to several photos of some tests I did with them. I sent the entire case back. I hope they are better now.
I got a chance to try it out at VF in 2005 and once again during a class that Randy G taught in my area. Pretty neat device and it was interesting. But then again, it was expensive!
There are other ways to get the same result if the money is not available (ghost ball aim trainer and Allison Fisher Billiard Aim Trainer).