I understand Mozilla's philosophical objections to the EME, but if the alternative is Flash/Silverlight (and it's pretty clear that is, in fact, the alternative), I don't think Mozilla's mission loses out by implementing the EME.
Of course there are others, but they hardly matter at all in terms of marketshare.
EME is a step down from Flash for consumer choice. A big fat one.
The problem is that copyright holders can still stipulate policies that exclude Linux. For example, http://voddler.com/en/ greets Linux users with "Here you can rent and play movies. For even more movies and TV-series, visit us from your PC or Mac, where we have a even larger selection."
(The really stupid thing is, I was trying to watch online streaming video that was available to the whole of the UK, with access controlled through IP geolocation. There was no need to tie decryption to a particular device ID in the first place. EME seems to be taking exactly the same approach though with support from Mozilla.)