I'm definitely with the smart dress/professionalism brigade. Guess I'm a natural tie-wearer (Latin geekus grosso)
However, when I used to work in/on/for our CCU I wore scrubs, purely because the unit was so warm, and scrubs really are soooo comfortable to work in!
Perhaps we should look at getting some scrubs with PCBs printed on 'em - that'd look professional, eh???