The Curse of Peladon is an extremely atmospheric story.  The faux-medieval trappings really work to build a picture of an alien and yet familiar society.  The dark torchlit corridors and almost stifling atmosphere really draw you into the story.

I've always loved Alpha Centauri and the collection of alien delegates are good value (even if Arcturus is a little silly).  Having the Ice Warriors turn out to be 'good guys' is a good twist and allows the Doctor to be seen as just as prejudiced as anyone can be.  It's a good choice for one of the most arrogant Doctors.

Less successful, maybe, are the rather cuddly-looking Aggedor and Grun, the King's Chamption, who I've never been able to take seriously (especially that silly up camera shot of him when the Doctor finds out it is Grun he'll be facing in combat.

It's a good story for Katy Manning too.  Jo gets loads to do including bossing the delegates around, throwing shade at the Doctor while pretending to be a princess and an actually pretty well written romance between her and Peladon.

Good, comfort Doctor Who.