When I saw it as a kid, I couldn't stand it. I remember eagerly checking out the next re-run of Star Trek and being really dejected seeing "The Way To Eden" come on.
I couldn't stand the clothing styles of the 60's and 70's. "Right on, man", "Far out", "That's so now"... all of those sayings--just couldn't stand it. The goofy plastic drivel songs that were written and orchestrated. Those big fat ugly American cars made me cringe anytime I had to ride in one. I was a 90's kid born a couple of decades too soon. 1990 couldn't come fast enough.
But TWTE has great nostalgic appeal to me now. Yeah, it's not my favorite episode, but there are plenty of qualities about the show that are entertaining. TOS is becoming a museum piece. The very fact that it laid down the foundation for the most successful science fiction franchise to date gives it added appeal. There was a time in the void between TOS and TNG that I'd started to lose appreciation for TOS. It was "the same old thing"... but not anymore. Still, there remains a handful of TOS episodes I hate to watch. If I could scratch off "And The Children Shall Lead" and "Wolf In the Fold" from my DVD collection without damaging everything else, I'd probably do it.