"I've seen the first show and I think it's sensational," he told reporters recently during a conference call alongside Lovato. "I think the girls do a great job and the contestants are great. The show looks different than anything we've ever made before."
Spears, specifically, will keep viewers on their toes.
"[She] is a fascinating person because you just don't know anything about her," Cowell says. "She's very unpredictable. You never know what is going to happen. She has taken this very seriously and she's surprisingly quite mean."
"In the past we've had judges that never say no," he continues. "[But] she can't say no quick enough on this show. She's quite difficult to please."
And fellow newbie, Lovato, is a fan of her colleague's judging style, too.
"I feel like the world hasn't gotten a chance to see her personality over the past couple years," Lovato says of Spears. "This is the perfect opportunity to see the light inside of her just shine. And she is very witty and funny and quirky. I just have such a good time working with her."
Unlike ousted former judges Paula Abdul and Nicole Scherzinger, Cowell likens Lovato and Spears to "having two racehorses who are very talented but very difficult to control."
"We have no control over these two whatsoever, and there are many, many times that we disagree," he says. "But that's what's made it more interesting this year. They are both unpredictable and have different and strong views."