Gilt City, luxury e-tailer Gilt Groupe's foray into local deals, has been quietly expanding in beta across the country in the past month or so, as we have written about here and here. Today the flash local deals site officially launches initiatives in New York, San Francisco, Los Angeles, Boston, Chicago, and Miami. While in the same social shopping space as Groupon, Gilt City's deals go live no matter how many people opt in. And while Gilt itself cultivates an air of exclusivity and is semi-invitation only, Gilt City is open to all. Another difference between Gilt City and Groupon? Gilt City promotes three or more sales in each city, which are live for about a week or until the supplies run out.