I personnaly feel I can be much more aggressive with a brake, so I keep it. I like to go fast, I know how to skip/skid, and this is what I do to stop and slow down. I nearly never use it and can not rememember when was the last time I used it. Just in case one day it can make the difference... I don't want to die on NYC streets. However, I think a fixed gear bike definitively looks better without a brake.
Last week in Lower East Side, an old guy stopped walking, looked at my bike and asked me (I was not riding) if it was a fixed gear and then why I had a brake... During one or two seconds, I felt stupid, but I know I feel safer with one, so I really don't care. "Emergency stops" was my answer...