I noticed that many folks who saw this animated series gave it scores like 9 or 10. Well, that is ridiculous, as the animation quality is just horrible--even by the low standards of the 1970s. So much of it looks like a terrible slide show and the ship the Enterprise encounters is a garish acid-trip sort of thing. As for the crews, the voices were the original characters but the animation made everyone look zombie-like! So, while the notion of being sucked towards a dead sun where a magnetic entity takes over the ship and, in essence, becomes the ship is interesting, the overall effect is severely muted due to Filmation's insistence that the show look like a pile of crap.
I would give the story a 6. It was reasonably interesting but underdeveloped. The dialog was rather stilted. The animation I would give a negative 4 if it was allowed, but IMDb likes scores between 1 and 10--so I'll score this a 1! Overall, a score of 3 seems reasonable and that's a bad indication as to what is likely to come in the next 21 episodes!