It most certainly works. Of course, you don't want to be too quiet; you'll just come off as a bit boring.
I've been reading a book on making a good first impression. One of the exercises in it suggested that I ask my friends and family members for feedback on my posture and thoughts on their first impressions of me. I felt like a bit of a douche when I was sending out my requests, but I'm actually quite glad I did it. I got to see how other people viewed me (assuming they were being honest).
Here's a description of the first impression I gave to a girl I met in college. Bear in mind that she didn't know anything about me, and saw me for the first time in class:
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you seemed really cold but in a cool way. Like one of those guys who would date super cute girls and your motto is "impress me".
She goes into some specifics about what gave her that impression:
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Well when you sat in class you looked really relaxed and cool and almost rebellious. The one thing you did was slum in your chair with your leg sticking straight out from your chair and you looked kinda apathetic. kinda like a bad boy
I rarely talked in class. She got all this just from the way I sat in my chair. I got a reply from a few other people that went along the same lines - quiet but confident. Your posture and body language says a lot to people. Even though you don't say a word, they can sense your confidence. As I said before, though, you want to make sure you actually open up well to people once they approach you. If you stick with your "strong, silent" routine, everyone will just start to avoid you.