Over all I thought season 13 was excellent. Really not a bad story in the bunch.
"Terror of the Zygons" was a solid story. The Loch Ness monster looked cheap but the Zygons and their sets were better. The tongue-like tentacle design of the Zygons themselves is pretty disgusting. Pity we don't see the Zygons again on TV until the 50th Anniversary special "Day of the Doctor".
"Planet of Evil" I couldn't find copies of the second and third parts of this but it's basically Dr. Jekyll and Mr. Hyde is space.
"Pyramids of Mars" is probably the classic Who story I've rewatched the most. It's excellent from beginning to end. Despite the robot Mummies looking a bit clunky Sutekh is one of the better villains of the classic series. "Kneel before the might of Sutekh!"
"The Android Invasion" The androids were creepy and the Kraals were kind of interesting. I wouldn't mind seeing them return to the new series. Plus Doctor doppelgangers are always fun.
"The Brain of Morbius" A Frankenstein-esque story with a talking brain in a jar. If that doesn't immediately sell this story to you I don't know what else will.
"The Seeds of Doom" starts off similar to The Thing complete with Antarctic base. The mood is creepy throughout and I find the plant life turned hostile theme to be pretty unsettling. I usually dislike the longer stories this being six parts it still managed to hold my attention. Tony Beckley gave a great performance as the villain Harrison Chase and the giant Krynoid attacking the house was a really cool visual.
Robot sure as hell ain't skippable.Tom Baker alone makes it worth watching.
I chose not to rewatch it after deciding to watch Tom Baker from the beginning. But yeah every fan should probably see it at least once.