She's one of the few "modern" pop artist whose work I like. "Hot N Cold" especially has that "classic pop" quality. "Part Of Me" is also pretty great--especially with the music video that doubles as a tribute to our men and women in uniform. (Props for that, in and of itself, I'd say!)
She also has an "innocent" quality--many times, when she performed on stage in SNL, I couldn't help but notice she looked a little unsure of herself, (her eyes bulging wide, clutching the mike close to her mouth), but still throwing herself into it. And when the audience cheers and applauds, she looks relieved that it went well.