I never did buy the remasters from iTunes; I didn't realize this version of Progress had already been released.  I'm mainly excited about it because it's the closest thing to new material on Essential Oils :)

I asked about Progress on the official Oils Facebook page and got these responses from the page owner:

"Progress is a composite of 3 different (original) mixes"

"Everything's been given a remaster but you will notice the difference most on the early tracks. The process involves going back to the original tapes (so for 1st album that was 1978 quarter inch reel to reel tapes), slow baking in a special oven to stop them shedding and then transferring to digital before remastering. The work was expertly carried out by Steve Smart at 301 and Midnight Oil's Jim Moginie."

"Yes it's the only one..."  (I had asked if Progress was the only track that had been given the extra-special treatment)

Robin.