I think the new feature might be reversible backleveling.
for instance: if you want to run LFR DS, you could backlevel to 85 and queue for it.
if you want to do a herald of the titans without rolling an alt, you could backlevel to 80 and run ulduar.
if you want to queue for some dungeons with your level 23 friend, you can backlevel to 23 and queue for LFD.
if you are in a future expansion and you really want the MoP challenge mode set, you can backlevel to level 90 and do challenge modes.