I would agree with Bdgregory, that it is hard to find a bad 'Junkies' CD. With that said, I also found 'Open' to be a bit of a letdown, with the exception of one track which is IMO Classic Junkies.
My personal favorite is Caution Horses. I agree again with Bdgregory that 'Lay It Down' is not often mentioned, is a good representation and is perhaps their most 'polished' offering. One track from it was in the soundtrack of 'The Truth About Cats & Dogs'.