I have actually been wondering the same thing.
There really doesn't seem to be any discussion about their material (except for the DAT). People seem to say it's decent and there is really no difference between the ace and royal flush edition.
But one thing that kinda of kept me from buying this is that if you look on amazon, they seem to have an amazing rating....but if you look at each of the people that posted it, those are the only feedback they ever gave for any item. Kinda of makes you think they had people post stuff there. Also, if you look at their 'testimonial' page on their website, there is a video of a girl 'reviewing' it but she looks as if she's having a really hard time keeping up with reading the script.
It just seems a little sketchy...can anyone shine light to this topic and let us know how it relates to the actual test?