If you already own the PiL albums, then you may have overlooked Plastic Box, thinking it a worthless Best Of… It kind of is(n't). It contains 4 discs, which is most of the first five albums minus half a dozen tracks (with some tracks from album number 2 replaced by the 1979 Peel Sessions - they're superb). The later PiL albums are less well-represented but they aren't very good anyhow. Elsewhere, you get some alternate 12" mixes, B-Sides, a few tracks culled from compilations and a film soundtrack, and finally the 1992 Mark Goodier Live Session. The early stuff is remastered and sounds fantastic. If you're new to PiL, it's the perfect place to start. If you're an existing fan, it'll have rarities throughout that'll make you very happy, but paying twice for stuff you already own is never fun.