It's hard to think that after a classic like "Mirror, Mirror" comes such a weak offering as "The Apple".
The common device of faceless redshirts being killed off had by now become a cliché of the series, and this episode matches "The Changeling" for the highest number (four) of on-screen redshirts to be killed. As per usual, nobody really seems to blink an eyelid – but as soon as Spock is nearly killed, it's panic panic!
In some episodes, the various details added to the planets make nice little background, but here, the poisonous dart-shooting plants (!) and the exploding rocks just feel like story padding, and it takes a long time for the real plot to kick in.
The Enterprise is having its energy drained by Vaal, not allowing the landing party to be beamed up or for the Enterprise to break out of orbit. The reasons for this never seemed to be fully explained; or more likely, I just wasn't interested enough to care; but either way, if they couldn't beam the landing party up, why didn't they at least deploy a shuttlecraft to pick them up?!
An unintentionally amusing moment comes as Kirk sneaks up on their watcher, Akuta, and thumps him in the face without even finding out if he's friend or foe; and then spends the next two minutes trying to convince the timid Akuta that he won't do it again!
The design, costume and make-up of the tribe are amongst the Original Series' worst. The men sport terrible white-blond wigs, and it is just not convincing to see pale white actors, daubed up in reddish make-up, trying to play scantily clad tribes people.
I am a 'Starsky & Hutch' fan, and the only (minor) point of interest for me with this lame episode is that David "Hutch" Soul has a small part as Makora, one of the tribesmen.
The story lacks any of the danger and urgency that it desperately needs, and personally I couldn't wait to get this one over with.
Some have compared this episode with "Who Mourns for Adonis?" – it is true they do have some similarities, but (while many people didn't like that episode), in that story I at least cared what happened. By the end of this one I was just bored.
The story has certainly been done before, but that's not the problem – this one is just so flat.
All-in-all, possibly the weakest of the season. For purists, watch once to say you've seen it and move on.