"They're great technicians, they have great ideas and they're just all around very, very talented," model and judge Heidi Klum says of Project Runway designers.

Think Project Runway is just a trend? Think again.

The designer sew-down has been channeling couch potatoes' inner fashionistas for three solid seasons. On Wednesday, it returns to Bravo for a fourth stroll down the catwalk.

Oh, and if you're not one of the millions already hooked, you might not want to start watching.

"It's like television crack," PR mentor Tim Gunn warns media on a teleconference he and supermodel host/judge Heidi Klum recently dialed into. "Once you start watching, you'll get addicted. I would never persuade anyone to watch this show."

Unfortunately for most PR viewers, it's too late. But at least those who can't live without their weekly fashion fix will be happy to know there's a new set of challenges on tap, and the talent is only getting better.

"With each successive season of Project Runway the group of designers has been stronger and stronger, and Season 4 is our strongest group yet," Gunn says of the 15 U.S. designers vying for PR's $100,000 payout and spread in Elle magazine.

Klum adds, "They're great technicians, they have great ideas and they're just all around very, very talented."

They should know. Klum and Gunn -- along with judges Michael Kors and Nina Garcia -- have been working PR since it premiered in 2004. Back then, style virtuoso Gunn had low expectations for the low-budget cable show in which the very first challenge saw the designers making outfits from grocery store goods.

"I'll just say that when we were taping Season 1 -- looking at what we were doing -- I thought, 'Who's going to really want to watch this?' " he says.

Millions, apparently. PR has been praised by critics as one of the less painful reality shows to watch. It has also spawned three relatively successful designers (Jay McCarroll, Chloe Dao and Jeffrey Sebelia), a trio of Emmy nominations, designer knockoffs like Project Catwalk and our own Project Runway Canada, and a signature catchphrase, "make it work" -- coined by the cynical mentor himself.

Klum says unique challenges and themes keep the show fresh, but the designers are the ultimate draw.

"I think people just truly love talented people," she says. "These designers make something with their passion, with their love, with their hands. This is really an art. It's the same as painters. It's a really hard job to break into and be successful in. For people watching, it's magical to see what these people do -- sometimes within a day and a $20 budget."

PR also packs its share of stress-charged drama -- with designers crying over split hemlines and tight deadlines -- and hauls in chic celebrity judges like Ivanka Trump and Debra Messing.

Klum and Gunn refuse to divulge what celebs are lined up for Season 4 (but insist Klum's hubby Seal isn't one of them). Klum herself prefers to go into the new season with a blind eye -- as she does every time she takes her seat on the judging panel.

"It's always a surprise," she says. "That's my favourite bit of the whole show ... When the model turns the corner and it looks amazing.

Or not."