If he, or anyone at that matter is building a strictly racing machine I would agree with you...who cares about looks as long as it performs and makes the car go fast.
BUT......... 99% of the people who mod their GP's are going to be lifting that hood to show off one time or another. Who the hell wants a nasty piece of PVC sitting there?? To each is his own, but I think it looks cheap and un-finished.
Boger: You on the other hand did a DIY job CORRECTLY! You took the time to get it right, prep and paint it, and it looks great! I'm not saying all PVC DIY intakes are cheap, I'm saying the ones that look like PVC are cheap.