[Nyororin]

I only attended 1 year at a school without uniforms...

Personally, while I can`t say I liked the uniform itself particularly - I do think it is a positive thing. People found plenty of ways to be be unique with accessories, and I saw much much less categorizing of people by their clothing styles.
Without uniforms, it seemed that groups were very clearly cut by what they wore, and people didn`t socialize much outside of those groups...