I'm not that familiar with them. I own Ghost Opera, which is pretty well composed and played but very jarring.
Jack Nicholson: "You can't
HANDLE Tan Dun!"
I'm not sure i understand the complaint that they're too commercial. To judge from their discography, the focus on the 20th and 21at centuries almost to exclusion, and are fond of commissioning new works from relatively obscure composers. That doesn't exactly scream 'box office gold' to me.
Well, they single-handedly launched Górecki into international acclaim; as Ken OC said, they have sold a lot of product; they did an arrangement of Jimi Hendrix' Purple Haze; they did an Astor Piazzola tango album; they eschew tuxedos, as their hairstyles and clothing, in cover photos, has been trendy;
What other horrible infractions of classical decorum could one want?
They are (shudder) cross-genre! According to WIK:
Kronos covers a very broad range of musical genres: Mexican folk, experimental, pre-classical early music, movie soundtracks (Requiem for a Dream, Heat, The Fountain), jazz and tango. Kronos has also recorded adaptations of Jimi Hendrix's "Purple Haze", Sigur Rós's "Flugufrelsarinn", Television's "Marquee Moon", Raymond Scott's "Dinner Music for a Pack of Hungry Cannibals", and Bob Dylan's "Don't Think Twice, It's All Right".
Kronos has also worked with a variety of global musicians, including Bollywood playback singer Asha Bhosle; Mexican-American painter Gronk; American soprano Dawn Upshaw; jazz composer/performer Pat Metheny; Mexican rockers Café Tacuba; Azerbaijani mugam singer Alim Qasimov; and the Romanian gypsy band Taraf de Haïdouks among others.
Kronos has performed live with the poet Allen Ginsberg, Ástor Piazzolla, the Modern Jazz Quartet, Tom Waits, David Bowie, and Björk, and has appeared on recordings with Nelly Furtado, Rokia Traore, Joan Armatrading, Brazilian electronica artist Amon Tobin, Texas yodeler Don Walser, Faith No More, Tiger Lillies and David Grisman.
On the 1998 Dave Matthews Band album Before These Crowded Streets, Kronos Quartet performed on the tracks Halloween and The Stone. They also appeared on the 2007 Nine Inch Nails remix album, Year Zero Remixed doing a rendition of the track Another Version of the Truth. They also performed Lee Brooks' score for the short film 2081, based on the Kurt Vonnegut short story "Harrison Bergeron."
In 2009, the quartet contributed an acoustic version of Blind Willie Johnson's "Dark Was the Night" for the AIDS benefit album Dark Was the Night produced by the Red Hot Organization.
By the time the quartet celebrated their twenty-fifth anniversary, in 1999, they had a repertoire of over 600 works, which included 400 string quartets written for them, more than 3,000 performances, seven first-prize ASCAP awards, Edison Awards in classical and popular music, and had sold more than 1.5 million records.
). At least once a semester, they do some sort of concert here, usually joint performances with someone else, for ex. guest artist dancers, singers or something like that. I've not seen them. They also do reading of new compositions made by the DMA composers at my university, I've not seen one of those performances yet. Always something else conflicting. 
