They seem like they'd be a medium challenge, but they're not. Getting them to print nicely on the paper is one thing, THEN making them look nice on a car is a whole nother set of problems. Gotta make sure it's a light enough color so it they can show up, or they won't.
The transfer portion seems like performing miniscule surgery. And may the customizing gods have mercy if you push too hard... with a wet cotton swab, cause there goes that decal.
Just my mini rant about trying to make my cars look good for the cameras. And I'm not starting in on my paint skill, or lack there of... Lol