Schools in the Netherlands don't have uniforms, but my school in Japan did. I thought it was nice that I didn't have to worry about what I should wear to school, but I did not like that there were specific days for changing into 'winter uniform' or 'summer uniform' and things inbetween without looking at the weather!
From the Japanese exchange student who came to the Netherlands, she said that at first she liked that she could wear her own clothes to school. But after a few months she said, "I wish there were uniforms here too", because she also had trouble deciding what to wear every day XD
People still express themselves even though they have uniforms, I noticed. They wear it in a different way, put things on their school bag so it differs from other school bags (our school uniform included a school bag) and they can do things with their hair and necklaces and stuff.