Affluent buyers from Silicon Valley have been scooping up luxury condos here, looking for places where they can crash after a late night at work, a dinner party or an outing to the opera....retired baby boomers and empty nesters who are trading their suburban estates for luxury condominiums in the city, and tech types who already live in the city and are cashing in stock and want to move up.....their kids are making a decision about where to go to college, and the parents are thinking about getting a place in the city and spending more time here."