I bought that album back when. My favorites are House Carpenter (cause I love those old, old folk tunes) and Brand New Sidewalk (great guitar, and that mournful bell sound near the end). The girl has a pretty voice, and I think they all are highly regarded as musicians (by more knowledgeable folks than I). Thile, of course, is a mandolin prodigy.
I wouldn't call them NewGrass, as I associate that with raping Bluegrass by turning it into long, drawn-out Grateful Dead jam jazz, devoid of soul. Or the homo-erotic wailing of that loathsome singer from New Grass Revival. I would say Nickel Creek is more of a Bluegrass-influenced string band that plays folk, folk-rock and bluegrass. Or something like that, at least on that album. Haven't kept up with them since then. Just avoid that song about the fox and the hen house, or whatever.