I was at the Bass Pro store in Springfield, Mo last week and found their floor model to already be showing wear on the top of the gunwhales. I have not seen any others close-up though to comment first hand. I have the 03 just before they painted and based on the marks/rubs on mine I do not see how the paint holds up or looks good after a few years.
I've had my '05 PT175 since Oct. '04, and the paint is holding-up fine. I use wax with UV protectors in it, and my boat cover is large enough that it covers the painted sides also. The wax also helps prevent abrasions/scuff marks [imo].