I suppose you can argue she's not really a seiyuu, but she's done at least one major (enough) role in anime, so I decided to list her under seiyuu catagory.
All of her songs have soft and peaceful feel to them, even the ones that are meant to be spirited. I think it's just her singing style, with some influence from her voice. Some people might feel that her songs lack dynamics, but I imagine most people won't have a problem.
Recording and mixing appears to be pretty good, but somehow, it's not as lively as I'd like. Then again, just not being annoying is worth an extra point, so I gave it a + grade.