I just downloaded it's pretty neat and clever. It's a mentalist feat that utilizes a very basic
mentalism principle. I have no idea why a reviewer would call this trick "Stupid". I wish he'd
clarify more. Even aside from the effect itself, the principle you learn is awesome and you can use
it to get your creative juices flowing. You'll need a bit of audience management as you don't want
them messing with your stuff.
One note, though the trick is free, you'll need a standard
card gaff. You'll find out what it is as soon as you order. This effect also works with the newer
bicycle card case only, but it's fairly standard now anyway so it shouldn't pose as a problem.