The online form for requesting information about the Flats at SouthSide Works allows prospective tenants to specify whether they want to move in immediately, within two to six months or within six months to one year.

The third choice is the only feasible option.

Spokeswoman Christie Fulton said the 83 rental units built into the Soffer Organization's mixed-used development are fully leased, and have had a high occupancy rate since their opening in January 2004.

With rents ranging from $1,000 to $2,800 a month, the apartments at the corner of 27th and East Carson streets have attracted young professionals and others seeking luxury digs in an urban setting.

For those who are concerned about Pittsburgh's ongoing population loss, perhaps the best thing about the Flats is that the majority of the tenants -- 60 percent -- are people who have relocated from outside the Pittsburgh area, Ms. Fulton said.

The exterior design of the Flats was created to match the neighborhood, which is dominated by three-story buildings with shops on their first floors and living units above. The SouthSide Works is home to a variety of specialty retailers and restaurants.

Inside, the Flats breaks with the tradition of building apartment complexes as collections of interchangeable boxes -- the apartments employ 27 different floor plans, including some with a two-story design that places the bedrooms on an upper loft.

Soffer is planning to add two condominium towers to the still-growing development, but Ms. Fulton said she could not comment on the expected timeline for their construction. Some South Side residents came out in opposition when Soffer announced last year that it wanted to build the condos to a height of 165 feet, rather than the 100 feet originally planned.

Most of the upper-floor space in SouthSide Works is not taken by residential units, but by office space. With three buildings offering corporate space above first-floor retail shops, and two buildings -- Quantum I and Quantum II -- dedicated entirely to it, the Soffer Organization's premier development has more than half a million square feet of office space.

Within a year of its ribbon cutting in September 2004, the complex had attracted tenants such as UPMC Health Systems and software developer Maya Viz, now a division of General Dynamic.

Industry observers have mixed views on the impact of SouthSide Works on the local office market.

"I think it's been very positive," Gerry McLaughlin, a senior vice president at Grubb & Ellis, said. "Without it American Eagle would never have decided to come Downtown." American Eagle Outfitters Inc. is relocating its headquarters from an office park in Marshall to the SouthSide Works.

The fact that the expanding American Eagle is also "a growing user of space" makes it even better, he said, "especially in a city that hasn't seen too many tenants in a growth mode."

Thomas P. Sullivan, a broker with Pennsylvania Commercial Real Estate Inc., sees it differently.

"All we're doing is reshuffling the deck," he said. "We haven't really attracted anybody from outside the region to locate in these new [complexes]. ... We're just robbing Peter to pay Paul."