The adaptivedemux base class has just been merged to gst-plugins-bad package and, with it, the first port of our 3 adaptive demuxer elements has also landed. Dashdemux is now only a thin layer of code that handles the specifics of parsing and keeping an MPD representation while the base class is the real adaptive client that does the fragment download and pushing among other generic adaptive features. (More on the base class can be found here: http://blog.thiagoss.com/2014/09/01/adaptive-demuxer-baseclass/)
Various playback tests have been done this month but some corner case may have escaped. So, if you test the new dashdemux (please do it) and happen to find a regression or any other issue report them at http://bugzilla.gnome.org/enter_bug.cgi?product=GStreamer. Bugs reported for DASH will have a very high priority on my TODO list for the next weeks. There are already some bugs open with patches for the old dashdemux version and I'm going to go over them and check if the patch can be ported to the adaptivedemux baseclass so those get fixed for all 3 formats for once (base classes are great!)
As for the other 2 demuxers (SmoothStreaming and HLS), we should be merging the port to the baseclass of one of them by the end of this week if nothing seriously wrong is reported until then. The other one will be merged in the following week. The rationale is that it allows some time for the code to sink in and obvious bugs to be found and fixed before having to test the next one.
Again, please test with git master so we can have a solid support for adaptive formats by the upcoming 1.6 release.
EDIT: mssdemux port has been merged in 04/12/2014