One of the problems of criticism is—what happens when it takes you just forever to realize that something is totally great? It took me until this week, and lots of it cropping up on shuffle, to realize that the latest PJ Harvey album, “White Chalk,” is absolutely her best. (Okay, second best—maybe nothing will ever be as cool as “Rid Of Me,” if only because who writes rock music in 5/4? ) Back in September, Pitchfork gave “White Chalk” a 6.8, and I would have given it a worse score even as recently as December. But of course, what does anyone know? “Uh Huh Her” got a 7.6, her Peel Sessions got a 7.9, “Stories from the City…” got a 5.5 and “Is This Desire?” got an Pitchfork 8.