the first question that springs to mind is would this be at home or in public?
Of course at home it's something that can be a real turn on, I personally believe a women in revealing clothing can be sexier than a women who is naked.
And if it's in public, it's hard to say, it often depends on the guy, if he is very self confident, he generally will mind less about his girlfriend wearing revealing clothes. but as Iamnotfrancis writes, it is very likely to attract often unwanted visitors. As far as talking about it goes, most women dress to impress other women, so ultimately the question is also do other women, find it sexy?