For a novelty design, they're not bad at all, really. Fes, you raise a very valid point about off-centered cuts on the card backs - but this isn't exactly the kind of deck that's going to sit on a pro poker table or most magician's close-up mats, in most cases. It'll be likely used by the kind of people who aren't even aware whether a design is one-way or not - and don't care because they think the fireworks look cool and the cards are colorful.
I've seen some decent decks from CPC and somer terrible ones. This looks like one of the better ones.