I just used protec duratec 600 on my boat, its a polyurethane enamel. Doesn't like the cold, dodgy compressors and has to be shot perfectly. Rubbing out orange peel is not an option. Adhesion and flexibility are the best I have used and its the most wear resistant paint have come across. Costs about $65 litre with hardener.
I wouldn't recommend it for home use but if you get a spray painter with a booth to spray it I doubt there is a better paint out there.
Darryn,
Bullet1782