I've just bought this at the weekend - and watched the whole six episodes in one go on Sunday afternoon(About 3 hours-worth). Well, there was nothing else on TV and I was hung-over, so decided to slob out for the rest of the day.(And warm-up the previous night's take-away).
What a joy it was to watch I grew up in William Hartnell's era, but don't remember this story/stories. It was obviously done on the cheap (as mentioned in commentaries and one of the 'extras' with the designer). But I found it to be such a fun-filled, dramatic and hilariously-unintended stories ever!
It was simply a six week adventure involving six seperate stories throughout...all interlinked by gathering the 'Keys of Marinus' at different areas of the planet (KEYS TO TIME anyone?).
The Doctor disappears for a couple of episodes, but they have new companions Sabetha (a pretty blonde woman) and Altis (a pretty young man flashing his legs in five episodes!).
Pretty cheap story - but fun to watch!
(You have to be a 'Classic Who' fan to appreciate it)

This was actually my first story. I remember as a small child after the "The Screaming Jungle" being scared to death because of the ivy we had growing on our house.

Marinus is a terrific story, and in places surprisingly 'adult'. Barbara at the mercy of the would-be rapist in the ice cave is chillingly effective, and I still think the Morpho are among Doctor Who's most creepy and underrated monsters.

I found the 'morpho' brains quite funny to watch - on the DVD - but I bet it scared the sh^t out of the kids at the time!!
I just don't remember watching it back then.
The Ice Cave was scary too....and that nasty man - he was obviously going to rape poor Barbara!
So innocent in those days....it went over my head (I was about 4 years old)

I watched this a few weeks back for the first time & i thought it was an alright story.The highlight for me but for the wrong reason is the last episode in which 1 of the actors playing a Voord nearly goes flying after he trips.