I haven't gone to art school in the sense of attending school with a schedule and grading and semesters and whatnot. I am self taught, and I believe that art school is useful if you want to socialize and enter the commercial art world (including fine art auctions and whatnot). It definitely opens the doors of financial opportunity if you are good at pandering or have some truly unique work.
I have attended classes at Cooper Union as a guest, and took some master courses at The National Academy School of Fine Art, around the corner from the Guggenheim. I have attended other classes in passing, which never stimulated my creative drive since these schools are more focused on techniques for rendering.
Personally, I never liked the environment, I didn't like Cooper Union, Pratt or the Art Institute in SF (where I lived for a while). I met a lot of aspiring artists. Many of which were nice people but terrible artists. My art school was Robert Crumb's work, living on the street/squatting/homelessness, drugs, alcohol, relationships with crazy women, the punk/skinhead scenes, the hip-hop scene. I was fortunate to work with well known artists (I don't drop names because it's tacky and I don't ride coat-tails), and to live vicariously through their experiences in the art scene. I was always content to be in the shadows and observe. Then I became Muslim around 6 years ago and this has definitely had a huge impact on the direction and evolution on my art. I was also an up-and-coming tattoo artist, but I sacrificed all of that for my new religion and it has had a positive impact on me as an artist, I am happy, best art school.
I figured I was an artist already, I never wanted to be, I was, and I already made it as an artist...