Aaaaargh!
To be fair, I hadn't seen any juddery images, although I do have a nice TV which does iron out a lot of crap (24Hz compatible TV, AMP and BD player have removed any jerky BD videos for example).
However, since Android Lollipop landed, my previously working (on 4.4.4) "Cast Screen" functionality has gone walkies. YouTube and other apps work, but I (and others, judging by the forums) can't cast screen anymore...
Way to go backwards!