Castrolvalva kind of blew me away, I had so much fun with it.  I very much enjoyed the Fifth Doctor post-regeneration.  It feels like it brings an edge and certain comedic flair I wish stayed true of the Fifth Doctor more in general, because this is some of the best Doctor I've ever seen Peter Davison perform.  I enjoyed the Master's scheme and various scenes with him having captured Adric really nicely played up the villain's evil plan.  Castrovalva was a very fun setting and I enjoyed the big twist around it.

So you have a fun little story and the new TARDIS crew really gives it all a strong sense of character.  You have creative ideas that nicely follow up on Logopolis and even add something new to the world of the TARDIS and Time Lords in the form of the Zero Room.  And you have the Doctor at his best, with a strong use of all three crew members.  The serial offers and lot and winds up being one of the better Fifth Doctor stories out of not just the televised set, but in general. Like I said, I really wish the Fifth Doctor acted a little more silly like he does here as I rather thoroughly enjoyed him on the whole in Castrovalva and he's a big part of what makes these episodes work so well.