I would say it is a must. The problem is society tells guys we are not suppose to care about how we look. So we have to try and look good, without letting anyone know we are trying to look good. Also a lot of guys don't really know how to take care of their appearance, because no one teaches us.
It's not everything, but it is important. It shows professionalism, common courtesy, and self-respect if a guy has good hygeine and at least some sense of style. Personally, I really like wearing suits. I used to not like it, but then, out of desperation for money, I took a job in a clothing store. I'm glad I did :)