I know this isn't really a bug, but Mojang removed "unneeded" datavalues of blocks like barriers or air.
The problem is that air with datavalue is a very helpful concept for mapmakers. For example invisible blocks that can turn into solid blocks: http://youtu.be/EhnqhmhEW0I?t=3m40s
In the new snapshots this concept is now impossible.
This datavalues are needed! Would it be a big problem to change this back?