Dress for Success is over used if you ask me. I can see it being important for first impressions, or when you are in front of clients and customers. Otherwise, I say, dress down and be comfortable.
Some companies have picked up along the same lines as my thinking with casual Fridays. In an article I read, "nearly three-quarters (71%) of the employers questioned believed dress-down days resulted in improved employee work performance."
I pose this question, what are you dressing up for? If you are going to sit in a cubical, or at a desk and have no physical contact with the outside world, whom are you dressing to impress? No one on the phone or email sees what you are wearing anyhow. As long as you are fulfilling your job and being productive, bring out the Hawaiian shirts!