I don't know of anyone who is a fan of Filmation, the company that brought Star Trek to Saturday morning. The reason is that it was guilty of the very worst crimes of cheap animation. Repetition of animation, bad drawings and designs, and just a sordid cheapness. The only reason there is anything good to say of Filmation is that would occasionally luck into a property developed by someone else. Such was the case in Star Trek. Basically Gene Rodenberry, a lot of his crew and most of the original actors came on board for about a season and a half of cartoons based on the TV show.
Now let's not get crazy with praise here. Every bad thing I've said about Filmation occurs here in spades. It's the type of cartoons that will have shots of the characters backs so as to not to have to animate lips. Still there are some very nice things here. First, being animation they were freed from limited budget of television production to some extent. They couldn't animate lips but they could draw incredible spaceships and aliens that at that time really couldn't be done for weekly television. I wish that the later series could draw off some of these designs now that they could be realized. It would be fun to see a race of three armed three legged dog creatures working for the federation.
More importantly, D. C. Fontana got some decent writers to get some stories down. Some worked for the show before, some where old hands with science fiction from magazines like Larry Niven. The Larry Niven episode was a lot of fun since he brought his own alien race, the Knitzes, to play with Kirk and the boys. The writing is definitely up a notch for Saturday morning and it helps a lot. There's a good mix of new stories, and revisiting some old friends. There's a good tribble follow up for example, and everyone remembers the one with Spock as a kid. Some might complain that there is a bit too many cliches here, but hey I was six when I first saw these, I had no idea what a cliche was. I like to think of it as a grand tarot of the major elements of science fiction.
Definitely worth a watch, and you might find some surprises. I forgot for example, that one episode clearly had a holodeck on the old Enterprise way before it caused trouble for Picard and his gang.