Britney Spears seems like a sweetheart, but she can sure get sassy at 'X Factor' auditions! While she's nowhere near Simon Cowell in terms of crankiness, the pop princess isn't shy about voicing her honest opinion when hopefuls hit the stage.

“Everyone was kinda shocked at how tough she was and how she wasn’t scared to say it straight,” a source told Entertainment Weekly about Spears. “She knows it takes more than having a good singing voice and that you have to be entertaining and have that ‘wow’ factor. She can really tell the difference between a good singer and a great performer.” As for her favorite criticism? "Too boring." Love it!

EW compiled some of Spears' best criticisms so far. She told one contestant, “I feel like you need to go to New York and be on Broadway. I don’t think the pop industry could handle you.” A lot of people said that about 'American Idol' runner up Adam Lambert, though, Brit -- don't be so sure!

Another contestant received, “To make a great performance, you have to step it up. There’s a big wall between us, and you need to learn to break it down.” That keeps in line with Spears' rep for seeking out performers versus vocalists. And that girl knows how to deliver an intense performance. She told another, ”I’m sorry, sweetie, but you have to be great to be on this show.”

The source went on to say that while Demi Lovato is chattier on the panel, all of the judges get along well and socialize in the green room and between takes together. Cowell's said to be "over the moon" about his decision to hire the two pop superstars (though he described them as "catty" and Lovato can admit to being "bratty"). Based on what we've been hearing about the upcoming 'X Factor' series, we are too.

Watch Britney Spears Arrive at the 'X Factor' Rhode Island Auditions