By Michelle Tauber
October 03, 2011 12:00 PM

The leaves are changing, the temperature is dropping, and Jennifer Aniston has swapped her flip-flops and tank tops for scarves and pea coats: Fall is in the air in New York City, where Aniston and boyfriend Justin Theroux have been kicking off the season with cozy nights in and relaxed date nights out. “She is having the best time with Justin in New York,” says a source close to the actress, who grew up in the city and is now renovating a condo there. Attending the launch of her stylists’ Hoyle Jackson Denim line at Bloomingdale’s on Sept. 16, the duo “were very comfortable with one another,” says an onlooker. At eatery Il Mulino afterward with a group of 10 friends, “they had nice chemistry,” says an observer. “They were always smiling.”

In love, eager to start a family and “on cloud nine,” as a friend puts it: These days, it seems, not much can dim Aniston’s famous smile. So when her ex, Brad Pitt, made controversial comments to Parade magazine about their marriage (see box), several sources close to Aniston say she took them in stride. In the interview, Pitt, 47, said that he “wasn’t living an interesting life” during his 2000-2005 marriage to Aniston, 42. In a statement, Pitt then clarified “not that Jen was dull, but that I was becoming dull to myself.” At the Sept. 19 Moneyball premiere, he further told PEOPLE that he never intended for the remarks “to be spun that way. People read things into it that just weren’t there.” Friends say that Aniston wasn’t upset. “Jen has moved on,” says one source. “She is in an amazing place with Justin now, and she believes it’s all meant to be.”

Those who know Aniston well say her romance with writer-actor Theroux, 40-whom she began dating in May after the pair worked together on the upcoming comedy Wanderlust-has shifted her perspective in many ways. After selling her 10,000-sq.-ft. mansion for a reported $38 million in June, Aniston downsized to a 1,700-sq.-ft. Hollywood Hills rental with Theroux. Last week they changed up coasts to spend time in New York’s West Village, heading out for shopping strolls and relaxed meals at restaurants such as EN Japanese Brasserie (that is, when Theroux wasn’t picking up takeout on his motorcycle). “Justin has definitely brought Jen out of her shell, and she seems beyond happy,” says the insider. “She feels more than ready to exit her comfort zone and to explore the world a bit more.” The actress is “truly content,” says another friend. “Whatever comes next is just icing on the cake.”