Recently, one of my friends called me a perfectionist.
(Relax, I wasn't offended-- I just didn't have anything worthwhile enough with which to reply.)
I don't consider myself a perfectionist. I'm sure all my co-workers are probably rolling their eyes and laughing hysterically right now. But seriously, I'm not a perfectionist. I make too many errors and am too prolific at work to be a perfectionist.
I do, however, think that you should make a real honest effort to do things properly as much as humanly possible. In certain fields, like web developing, this isn't an unreasonable expectation. There are tools you can run on your web pages to make sure the code is valid.
It's not my fault if no one else in my area bothers to run their code through a validator-- or still uses nested tables to control their layouts because they can't be bothered to learn about div tags and CSS.