I've already mentioned this, at least somewhere because it's hard to keep track on which forums I've posted to.
I purchased the US version from Amazon.com on July 6th resigned to the fact that I'd end up getting the inferior MPEG version. I thought that as it was only $9.99 plus postage I could live with it until the 'best' version was released.
When it arrived I was amazed to find it was an AVC encode. My first thought was that I'd struck lucky in getting one of the AVC discs. However when I checked it out I found that the colour timing had been corrected (easiest shot to compare was the shot of the group photo outside the cabin. The scene now matched the one on the AUS version. Other scenes were also found to match.)
Further checks revealed that the contrast had also been corrected (the black levels are now correct in the cave scenes whilst still preserving detail into the darkest recesses, but not as 'dark' as the AUS version by its overuse of the contrast control so wiping out lots of low level detail.)
Colours are also stronger in the styilized scenes (when the caves are lit up in red for example) than on the original US discs, but they're not quite as strong as the colours on the AUS version which I think are a bit OTT to be honest (and, along with the contrast issue, the reason why I didn't get this version.)
Further, someone posted that his recently acquired (at the time he posted 3 or 4 months back) US AVC disc had the same corrections as to what I have found above, but I think people dismissed him as he was the only one stating it at that time. So from my findings (and his) I do conclude that Lionsgate have at some point quietly re-released it yet again, and that this version is now the best of the four so far.
Finally, it must be said that if I was looking to buy the disc now I would wait until the UK disc is released to see what that is like and what extras are on it. Doing so would also avoid the lottery of which US version of the three you'd end up with, though chances are you'd end up with this corrected one.