No, never. Sometimes I'll change my style during a relationship, and maybe those changes could happen because of something my partner made me realize, but never just to compliment his style. I'm very comfortable with my own style right now. I also usually find that the people I date either don't care about my style or are attracted to it, never someone with a contrasting idea of dressing, necessarily.
I agree with what most of you are saying, though, that I will change my style slightly for formality, but that has more to do with the place than the person, I think. I've just always dated people with relatively similar interests and all that, so it's almost always meant that we enjoy going to the same events. I think if a man ever compels you to dress differently (unless it's something revealing, or just something he disapproves of beyond just a superficial nature) he should be tossed. At least that's what I do. My style is a reflection of my personality and my tastes, and if someone disapproves, it's not likely at all that we'd be a good match.