I bought this after hearing it in Urban Outfitters (where it's only £15, by the way) and was instantly hooked. These guys take hiphop/rap tunes and lay the lyrics over pop songs, creating (mostly) better versions of the originals.
Production is slick and the choice of songs is brilliant - there's a bit of everything to suit all tastes (I rate the hiphop while my girlfriend bobs her head to the chart pop background), making it good for putting on when you've got people round for the night.
Only down side is that there's one or two questionable tracks that I skip each time I listen to the album, but only one or two. Overall this is definitely worth buying, and will keep you entertained for aaaages.