I recently went through "The Sea Devils," "The Time Monster," "Carnival of Monsters," & the 1st 4 parts of "Frontier in Space."
"The Sea Devils" isn't as good as I remembered. Roger Delgado is good as always. But the Sea Devils themselves are hardly in it. And it feels weird to see the Doctor constantly butting heads with an incredulous military figure that isn't Lethbridge-Stewart.
"The Time Monster" was decent, although I wish more of it had taken place in Atlantis. And while the bit with the two TARDISes being inside each other has some nice echoes of Moffatt's "Space" & "Time" shorts, it makes a little bit less sense because, at one point, it seems that the exterior of the Master's TARDIS is both inside the Doctor's TARDIS and in the science lab at the same time. (Although, "Zagreus" implied that TARDISes have a back door as well, so maybe this is some kind of multi-dimensional equivalent.)
"Carnival of Monsters" is a lot of fun. No one writes conniving guest stars with their own contrary agendas like Robert Holmes. And Peter Halliday will always have a soft spot in my heart.
"Frontier in Space" has a lot to recommend it. Although it's a 6-parter, it breaks it up quite a bit by taking place in many different locations (even if half of them are just jail cells that the Doctor & Jo keep getting marched to & from for most of the story).