The 2.0 MKV has a lot more audio tracks. I imagine one could remux a different audio track into 2.5 if they wished.
Also patiently waiting for the "3.0" action, though with getting menus involved, I only hope it's not something too tedious/messy to make happen. I think that once the final file is done, adding a quick menu, adding the slideshow(s), etc. it shouldn't be too hard to build, though blu ray authoring seems like a lot more of a PITA than DVD is/was.
Also very exited to see a "matching" set of updates for ESB/ROTJ some time after this gets the final touches. The Hoth test clip looked pretty good. Will comment over there at some point with my thoughts on that.
...not sure what # we're on now, but I'll go "one louder" than whatever the last # was for an audio featurette.