I'm not savvy enough to know what all the differences are DC, but if you jump on some current ones i think you will notice quite a difference. On the 27m GS skis the earlier ones were often a bit of a bear to start the turn. Example, the 2009 Blizzard GS 27m 185 was superfast but I was simply not good enough/strong enough to get it into the turn consistently. A bit like the 2002, 2003 21 m GS skis were a bit dead. This season i have been on the 2011 Fischer GS in 188 and 183 27m and found absolutely no issues getting them to respond and them being skiable. In fact after using them I got rid of my 23m versions. i suspect it has been a process of evolution which has effectively led to the 27m skis being as easily skiable as the earlier >21m ones. Also D2 on the Atomic GS seems to work pretty well and a similar power deck on the 2012 Blizzard (haven't skied it but some reports have suggested it makes the Blizzard too dead which is unfortunate as the 2011 Blizzard GS is a great ski)
On slalom, it is harder to nail it down but some of the improvements I have found have been the Atomic D2 SL with the "control deck" (i.e extended plate...) and the Rossi/Dynastar slant nose which is a helluva ski, lots more pop than anything else I have skied. Can't speak to the Volkl changes (Speedwall?) as the last one I skied was the 2008 Sl which just didn't work for me.
Edited by ScotsSkier - 5/3/12 at 10:19pm