None.

With its many (five at my last count?) different alien species, its verdant and violent jungle, and the amazing ice volcanoes (real things! But surely not right next door to a tropical rainforest...), this was not the story to be landed with a miniscule budget. None of it convinces. Literally none. The bit that sticks with me—in fact the first thing I think about when someone mentions this story—is "dawn" on Spiridon being signified by the sudden turning on of a single studio light. Awful.

This is not the first nor the last time the series has resorted to invisible aliens as a result of no money, but amazingly, these Spiridons are a hundred times worse than the Visians from eight (I think) years earlier. The evolutionary advantage is clear, but then draping oneself in a purple rug, or waggling a stick around un-threateningly, surely negates that. The natives are simply ridiculous. The Thals, led by Bernard Horsfall in what feels like his 250th appearance in the show already, are a little better, and everyone knows the issues with the Daleks. I would only like to add to it how the controls in their HQ are clearly impossible for them to use. And another favourite moment: Jo is so distraught at the Doctor's predicament...that she changes into a brown trouser suit. That'll help.

This is a hugely ambitious serial, and despite tearing it to shreds, I actually quite like it overall. It's this sort of story that makes me think maybe for an anniversary year they should re-do some old ones. With a workable budget and some more creative minds, I expect this could be thrilling. As it is, it's at times comical, but still very easy to watch.

EDIT: Deleted my comment because I posted on the wrong discussion post

Does nothing to really tie in to prior story. And Terry Nation is Clearly running out of ideas.

For the most part, this is just a dull, overlong, generic and utterly forgettable Daleks story which is where Terry Nation's frustrating trend of recycling prior material really began to take shape, and is easily the worst story of what is otherwise a phenomenal season. However, there are two issues about it that irritate me above all else, which are both related to its connections to Frontier in Space:

1. Despite supposedly continuing directly on from Frontier in Space, no characters or plot strands from that story come into play in this one in any way, and all the information the few returning characters gained from Frontier in Space is seemingly forgotten for no apparent reason, with the Doctor somehow being surprised that Spiradon has Daleks on it despite Frontier in Space ending with him instructing the Time Lords to take him to the Daleks' base of operations (one of many reasons why the Dalek reveal cliffhanger at the end of episode one is laughably ineffective).

2. And on top of that, after spending 12 episodes across 2 stories dedicated to this particular plotline, it still remains unresolved by Planet of the Daleks' conclusion, with the Dalek Supreme explicitly stating at the end that "We have been delayed, not defeated", only for this plot strand to never be so much as acknowledged within the show ever again, essentially making the past 5 hours a giant waste of the audience's time.