Dress for Success, a recent article on careerjournal.com (the online career arm of The Wall Street Journal), reports on a survey about how a worker is perceived based on how he or she dresses. It's no surprise that the survey says those who dress in suits (rather than more casual outfits) give the impression that they are more senior level, taken more seriously, trusted more, more rigid, and less creative. (Can't say I'd want the last two tags on me.)
This, of course, doesn't necessary apply to companies like Pixar where most employees dress in jeans everyday and glide on razors from their spacious cubicles to the gourmet cafeteria, which happens to be next to the pingpong tables. But in the "other real world" dress does seem to matter, even to the point of supporting a higher paycheck.
So, when you go on that job interview, be sure to wear something a little better than your fancy jeans. Actually, I recommend you scout out the company to see what the normal dress code seems to be; then dress one notch higher for your interview. That way, you'll demonstrate that you'll fit in with the company culture.
And when you meet with your boss for your yearly review, I suggest you dress a little better than usual that day. Hey, maybe you'll look like you're worth more $$!