Way back in the 1990s, I started going to the South by Southwest music festival in Austin, Texas.

Every March, I'd go back to find not only that the festival had gotten bigger and bigger - too big, it became clear this year, when four people were killed by a runaway drunken driver - but also that the city was mushrooming along with it.

In Austin, the livability factor is high - warm temperatures, live music, BBQ - and the stream of transplants so steady it doesn't take long for new residents to start moaning about how everything was better before people who arrived after them came to town.

Which brings me to the latest indicator that everybody has figured out Philadelphia is a cool place to live. It's the modeled-after-SXSW Forbes Under 30 Summit, the money magazine's inaugural gathering of boldface billionaires and tech titans (and upstart entrepreneurs who wish to emulate them) that will take place in its planned-to-be permanent home from today until Wednesday.

The event, which promises to bring "the world's brightest young game changers" to town, is eye-catching. It kicks off Sunday with the Under 30 Music Festival at the Piazza at Schmidts in Northern Liberties, with weed-happy rapper Wiz Khalifa and Dutch deejay Afrojack, plus New York songwriter LP and Philadelphia rap duo OCD: Moosh & Twist. It's a free show, with gratis tickets given out through the antipoverty organization Global Citizen.

The big-shot list at the Convention Center impresses: teenage Nobel Peace Prize-winner Malala Yousafzai (in town anyway to pick up the Liberty Medal at the National Constitution Center on Tuesday) plus bosses like Sara Blakely of Spanx, Peter Thiel of PayPal, Sean Rad of Tinder, and former Lady Gaga manager and West Philly native Troy Carter.

Questlove will spin at a Tuesday-night cooking competition at the Troc, and an intriguing panel on Monday called "Music Goes Moneyball" will explore how Big Data shapes listening habits.

What got my attention, though, was the "Why Philly?" section of Forbes editor Randall Lane's explanatory note.

"It was the only city we considered," he wrote. Convenience is part of it - it's easier to get here than far-flung confab spots like Aspen or Davos, Switzerland. But there's also this: Philadelphia is "a world-class city in every way - great food, history, business vitality, nightlife, and culture - as validated this year by everyone from Jay Z to the pope."

A Philadelphian's reflexive reaction: "Really? Is he talking about us?" (A second, equally appropriate take: "Do world-class cities have tragically underfunded public schools, or a murder rate in which the 206 homicides this year, according to PhillyPolice.com, has already surpassed the 194 in all of 2013?")

But, yes, he is talking about us. And as far as the food, history, nightlife, and culture part goes, he's not blowing smoke. (As for business vitality, check out Erin Arvedlund's column on Philly as a start-up hotbed, elsewhere in LiveLifeLove.)

Lane's seal-the-deal reason to commit to Philadelphia? "It's America's fastest-growing city for millennials."

That finding is from a 2014 Pew Charitable Trust study showing that since 2006, no major city has had a larger increase in 20-to-34-year-olds in population percentage. (Let's note, however, that the percentage increase of young adults is that high partly because we started so low, and Philadelphia is now close to the median, at 26 percent.)

Let's talk anecdotal evidence. With mobile technology giving people more options to live where they want, Philadelphia is a reasonably affordable option for creatives, which is where all the superexpensive "supercities" on the East Coast lose.

How do we win? With a music scene that's better than ever, with touring bands like Strand of Oaks, Dr. Dog, and the War on Drugs garnering national attention, and the Roots on The Tonight Show repping Philly on national TV every weeknight.

Used to be the only people you met in Philadelphia were from Philadelphia, or maybe an exotic locale as distant as Lancaster County. Now Jay Z's Made in America festival happens every year, and, yes, Pope Francis is headed to the 215 in 2015 for the World Meeting of Families. My goodness, it's even rumored that Philadelphia is the next destination for Bravo's Real Housewives series.

As my colleague Craig LaBan has chronicled, New York chefs like Peter Serpico and Greg Vernick have either emigrated or returned home here to open acclaimed restaurants. A beverage-industry insider I met at SXSW this year confirmed what my own pub-crawling research has told me: Along with San Diego, Philadelphia is the most sophisticated beer market in the United States.

The indie-band boom in town is also partially fueled by musical immigrants, originating elsewhere but based here now. The power-pop quintet Cheerleader, at MilkBoy on Wednesday, is from Connecticut. Katie Crutchfield, the songwriter who performs as Waxahatchee, will play two shows at the First Unitarian Side Chapel on Nov. 9; she hails from Alabama.

All these lifestyle victories - the Schuylkill Banks Boardwalk, the ESPO mural in the new La Colombe coffee shop in Fishtown, the Alex Da Corte & Jayson Musson video show "Easternsports" at the Institute of Contemporary Art - are good for Philadelphia, right?

Of course they are. And add to that only-in-Philly list this fall's Pennsylvania Academy of the Fine Arts exhibit "David Lynch: The Unified Field," dedicated to the Blue Velvet filmmaker's career as a painter, begun when he lived in Philadelphia in the late 1960s.

Lynch has long been on record about Philadelphia as his lifelong muse: "An artist couldn't ask for anything more. It was a gold mine, it was so beautiful," he has said. In the show notes, Lynch waxes nostalgic about how 1960s Philadelphia had "a great mood - factories, smoke, railroads, diners, the strangest characters and the darkest nights. The people had stories attached to their faces."

That's enough to make you nostalgic for the Gothic, grimy Philadelphia, and it's a reminder of how much the destination city for Forbes' Under 30 entrepreneurs this week has changed.

Which it will continue to do, no doubt, as the word on what a cool place Philadelphia has become continues to spread until - inevitably - the complaining starts that new arrivals are ruining it for everyone who remembers what it was like in the bad old days.