Review of all 6 episodes:
This is a fun and mostly decent standard production providing tense and exciting Cybermen attacks and the arrival of a good new companion Zoe. (Previous companion Victoria having just left and featuring only in a clip at the start of Episode 1)
This story is written by David Whitaker from a story by Kit Pedler. Whitaker's script provides good dialogue and tense scenes but Pedler's plot is unremarkable and does not all make sense sadly. Some of the science is not as realistic as it could be (the meteorite sequences etc) and the Cybermen's plan is not entirely sensible or believable. It is not as awful as some would have you believe and the issues certainly do not make it a totally unsuccessful story but they do take the silver sheen off of some of this adventure as it lacks a bit of credibility and originality. It still is mostly solid, entertaining stuff. Part 5 is the least good featuring more of the silly aspects.
The Wheel in Space is largely an enjoyable romp with some excellent elements but it is unexceptional and looks weak by comparison to the truly brilliant stories preceding it in season 5. The Cybermen voices are, in my opinion, far inferior to their original voices from The Tenth Planet or from some of their later incarnations.
My Ratings: Episodes 1, 2, 3 & 6 - 7.5/10, Episode 4 - 8/10, Episode 5 - 6/10
Overall: 7.33/10
The rest of Season 5 was far better than this rather anticlimactic final story. Easily one of my top 5 Doctor Who Seasons of all time, truly fantastic quality.
Season 5 Average Rating: 9.26/10