If you have the money and the time, go to school. It's fun and you'll learn a lot. I would agree that in photography your portfolio and job experience probably is more important than a degree in the long run. But school has a lot of good things to teach about the business aspects, and they will probably also help set you up with a good assistantship when you are done.
I didn't go to an art school, but I have attended many photography classes at a university with a large photo dept. There is no doubt that I've taught myself more about photography on my own than I learned in school. But it was a lot of fun, and they'll teach you a thing or two.
I don't think that school is a detriment on your resume, although work experience will definately hold more weight. Depending on what school you go to, you may be exposed to fantastic work opportunities that you'd only get with the school's help.