I don't think dressing up shows you care about anything. It just means you read an outdated page on monster.com about proper interview etiquette in an industry where nobody cares about that. And it might mean that you are a follower and not a leader, so you can't think for yourself (not a plus in this industry, btw)
I mean, if you're applying for a job at the FBI, or a bank, or an insurance company, maybe. At a tech company, I don't see it.
20 years ago, I got my first job when I posted my resume on a usenet group from a ridiculous email address like
satan666@hotmail.com. I later found out they contacted me *because* my email address was so hilarious.
Job after that, I wrote a scathing review of a technical book on amazon.com, very informally, and got emailed because they liked my review.
My last job, I wore jeans with a big hole in the leg and a gaming t-shirt (was an interview at a game company), and we talked about how awesome that game was over lunch.
Seriously, nobody cares what you're wearing. I promise you. And if they do, *that* is the type of company you don't want to work at.