Taylor Swift was the headliner at the Formula 1 US Grand Prix Saturday night concert at COTA in Austin a few years back. I'd heard her music because my then-10-year-old daughter liked her, and I thought it was pretty good. Since we get tickets for the race specifically, I always view the concerts as essentially "free" and so we went to the concert, because it was free.
I have to say, it's one of the best concerts I've ever attended live.
I guess her voice isn't "unique or special" but it's certainly very good, even live, and she's a heck of a songwriter. She's also an excellent live performer, her connection wtih an 80,000 person audience, was remarkable.
Anyway, yeah, she's a superstar. Madonna/Michael Jackson/Prince/Elvis/Beatles kind of big.