NOTE: the following is a review I wrote on another website back in 2003 - it's more-or-less the same review with some minor corrections for things I've since learnt over the years.
I was 6 when I first saw this version of The Wizard of Oz, and at the time I hadn't seen any of the other versions nor even knew it was actually based on a book. Only afterward did I get to find out it was based on a novel (which I have never read) and see the Judy Garland version plus the 'Return to Oz' movie released in the 1980s.
Needless to say my memory is a bit sketchy, however I can remember enjoying this one immensely (my local TV station ran it twice - restarting it as soon as its first run finished). One thing 'The Wonderful Wizard of Oz' has over some of the other versions is its length - it was able to be spread out over many episodes and not have to be crammed into a 2hr movie or something similar.
From my own experience I considered the story as being divided into 3 parts (I've since found out that it was officially considered 4 parts). The first part concerned to most memorable part of the Oz saga - Dorothy getting sucked up by the tornado only to land in Oz, where she meets up with the Scarecrow, the Tin Woodsman and the Cowardly Lion. They all join together in a variety of adventures as she attempts to get to the Emerald City to meet the famous Wizard who supposedly has the power to return her home. The Wizard instead sends them off to kill the Wicked Witch of the West (which they do) but upon returning it is discovered the Wizard is in fact just a normal man who arrived in Oz via a balloon. When Dorothy misses out on returning home with the Wizard she and her friends end up going to meet Glinda the Good Witch of the South (interestingly every other version I've seen has Glinda as being from the North) where Dorothy learns that she only needs to click her magic slippers to return home.
The second part involved characters such as the witch Mombi, the usurper-of-the-throne Queen Jinjur (the throne had previously been held by Scarecrow after the leaving of the Wizard) as well as the memorable Jack Pumpkinhead and his master/guardian Tip (who later turned out to be Princess Ozma disguised by magic as a boy by Mombi). This part ended with Ozma being revealed and taking her place on the throne of Oz. I have to admit I'm a little hazy on what happened during this part with the exception of Jinjur making herself Queen after Dorothy and co escape on a wooden horse (brought to life by Tip with the same magic powder that created Jack Pumpkinhead) as well as the end where Ozma is revealed and crowned.
The third part struck me as the strangest (and somewhat boring) part involving Dorothy visiting the land of Ev and meeting characters such as Tick Tock and the Nome King. This part ended with Dorothy ending up back in Oz and the Nome King launching an (unsuccessful) invasion of the Emerald City. One of the most memorable parts from this one was the ornament room where the correct ornament had to be chosen lest the person themselves be turned into an ornament ('Return to Oz' used this part too). At the time this part of the story struck me as the weirdest as I never really understood how Ev existed alongside Oz (I've since learnt that it was a neighbouring nation-state). I was also bored by it a bit as most of the storyline took place in Ev (which is more or less a desert). Fortunately the later sequences in Oz were more enjoyable, especially with the constant girl-fighting between Dorothy and Ozma (who had turned into a bit of a spoiled brat between this part and the last part when Ozma was Tip).
(as mentioned previously, officially the series is divided into 4 parts - the final 2 sections (Part 3 in the land of Ev, Part 4 back in Oz with the Nome King invading) making up what I considered the third part above. Despite this knowledge I prefer to count it as one single entity as that was how I saw it as a kid)
All up it was an enjoyable series for me and I have plenty of fond memories of it. At the time I didn't know how close it resembled the original novels (turns out the first part is fairly close; the second part is close as well but the novel didn't feature Dorothy; the third and fourth parts deviate the most by taking a number of liberties with the storyline from the books) but compared to some of the other attempts at bringing the Oz story to the screen (big and small) this one is good for taking the time to develop a nice, long story with characters who flesh out and grow as the series moves along.
Definitely recommended for anyone who enjoys the Oz universe.