I would say if the condition of your current paint is really good, then it could be worth it. I wouldn't ceramic coat paint thats fading or has a bunch of imperfections though.
What are the advantages of ceramic coatings?
I did the diy with the magires stuff per dirctions, was not impressed but reapplied it per directions and still not impressed, dust maganet and not smooth feeling, hand wax is my weapon of choice, dusty, quick drive down the street, dust gone.
Feels slick and clean like glass, lasts long time.