In my humble opinion, $100 is a pretty steepprice for this product, considering that's 1/6th of the price of an E-500 two-lens kit. Similar split focus screens have been available on eBay from reliable sellers for months now for the E-500 at 1/4 that price.
I have not heard anything bad about the Katz Eye products. In fact, they always are highly recommended everywhere I've seen the name mentioned. However, there are signficantly cheaper solutions already available.