I used to proudly wear nice close when attending church. You know, a collared shirt with a vest and khakis. But when we moved to the town I am in now when I was 10, we started attending a less formal church (it is a semi-mega church). Most people there would wear a t-shirt and jeans, so eventually I stopped wearing formal attire.
HOWEVER! I still think people should wear nicer close to church. I wouldn't on Sundays because I help with 4-5 year olds and would likely get my nice clothes dirty in that setting (markers, play-doh, snack crumbs etc.). But sometime in the future, I want to go to church wearing my debate suit, and see what people think. :P