I really enjoyed the last episode- it was interesting to hone in a bit more on the "main four" characters, as often Gwen or Morgana is forsaken for the other.
Morgana is fully fledged "evil" now, whatever Morgause told her on her year away, it's festered right into the centre of her, encouraged by her bitterness towards Merlin. She's nearly killed Uther before, and gone behind her friends back in the last series, but now we're seeing traits in her that are only being fully uncovered now; she's determined- whatever the costs- to get the throne, just as Uther is determined to keep it, whatever the costs. I read a very, very interesting spoiler though for the end of the series (although it was hinted at very overtly in the Crystal Cave episode.)