Sept 2011 Magpie and Model are more "shimmery", albeit very very fine shimmer.
Jan 2012 Fusion and Propinquity are smooth sheen-ish, if that makes sense. Like lit from within.
I have my Model pressed (although I still remember vividly that its finish pre-pressing was exactly as loose Magpie) and swatched the other 3, which I haven't pressed yet, loose and damp.


Propinquity and Fusion in the second picture were swatched damp with FCO to mimic its finish after pressing.
I hope Karen can confirm if there's a change/difference in the formula. I like the finish of the "newer" version better, but much prefer the "older" formula because when I press them, the finish will exactly be like the "newer" formula.