The Citi Bike bicycle-sharing program launched yesterday with about 6,000 trips taken by late afternoon. The privately funded program offers 6,000 bikes from stations in Manhattan and Brooklyn. Only those signed up for the $95 annual fee can ride them this week, which so far is around 15,000 people. It's already the largest system in the country, and will expand to 10,000 bikes with stations farther uptown, deeper into Brooklyn, and in Queens. One of the bikes was stolen as workers were delivering it to a station. A Daily News reporter took one for a ride and called the bike heavy and sturdy, and smooth but not quite fast. There were glitches with the racks, with bikes easily taken out without a key or unable to be returned. And the smartphone app didn't work yet. A protest was also held at a station in SoHo which is reserved for art.