I'll say right off the bat that the effect is very gimmicky. But I assume most have suspected that
already. The trick is not hard to do, but it takes practice and effort to make it look smooth and
natural. You have to be careful with the card gimmicks, but you can't make it look like you're being
careful, or else you'll draw suspicion and the illusion is shattered for all practical purposes.
Due to the method involved, you will need a soft surface to work on. So I don't put it in
the "anytime, anywhere" category. I consider it more useful for controlled and formal environments.
There's also the issue of trying to make it look organic and natural. In other words, how do you
justify taking eight cards out of a little wallet, as opposed to just removing them from a regular
deck. That, coupled with the fact that they're not examinable, can be a presentational challenge.
There are solutions to these "problems", but I wouldn't recommend this to beginners at all.
Stick to clean, organic, examinable stuff if you're new. But more experienced magicians can find
value in this. Oz makes it look so easy, but it takes work to get it down. It's not technically
hard, but you have to remember the steps and work on making it look natural.