See for me, the Holodeck fell completely flat. Part of it is that I see it as the one great technological leap separating TNG era from TOS era - so it doesn't belong in a TOS-era series. Not in my opinion, anyways. Also, and this is a big complaint, it did nothing for the story. Nothing.
It threw me off track. When they were debating on whether or not it was safe to find a planet for Apollo to live out his remaining days, I thought the Holodeck was going to come into play. I figured they would somehow use it to give Apollo the illusion of a settling on a planet.
I have no idea why it was even in the episode other than to establish its existence for possible use in a future story.